[ADT] Add implementations for avgFloor and avgCeil to APInt #84431

Atousa · 2024-03-08T05:31:52Z

Supports both signed and unsigned expansions.
SelectionDAG now calls the APInt implementation of these functions.

Fixes #84211.

llvmbot · 2024-03-08T05:33:37Z

@llvm/pr-subscribers-llvm-selectiondag
@llvm/pr-subscribers-llvm-adt

@llvm/pr-subscribers-llvm-support

Author: Atousa Duprat (Atousa)

Changes

Supports both signed and unsigned expansions.
SelectionDAG now calls the APInt implementation of these functions.

Issue #84211.

Full diff: https://github.com/llvm/llvm-project/pull/84431.diff

4 Files Affected:

(modified) llvm/include/llvm/ADT/APInt.h (+12)
(modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (+8-24)
(modified) llvm/lib/Support/APInt.cpp (+36)
(modified) llvm/unittests/ADT/APIntTest.cpp (+50)

diff --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index 1fc3c7b2236a17..72f88fd956f2f3 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -2193,6 +2193,18 @@ inline const APInt absdiff(const APInt &A, const APInt &B) {
   return A.uge(B) ? (A - B) : (B - A);
 }
 
+///.Compute the signed floor of the average of C1 and C2
+APInt avgFloorS(const APInt &C1, const APInt &C2);
+
+///.Compute the floor of the average of C1 and C2
+APInt avgFloorU(const APInt &C1, const APInt &C2);
+
+///.Compute the ceil of the average of C1 and C2
+APInt avgCeilS(const APInt &C1, const APInt &C2);
+
+///.Compute the ceil of the average of C1 and C2
+APInt avgCeilU(const APInt &C1, const APInt &C2);
+
 /// Compute GCD of two unsigned APInt values.
 ///
 /// This function returns the greatest common divisor of the two APInt values
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index f7ace79e8c51d4..a844a00be16291 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6021,30 +6021,14 @@ static std::optional<APInt> FoldValue(unsigned Opcode, const APInt &C1,
     APInt C2Ext = C2.zext(FullWidth);
     return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());
   }
-  case ISD::AVGFLOORS: {
-    unsigned FullWidth = C1.getBitWidth() + 1;
-    APInt C1Ext = C1.sext(FullWidth);
-    APInt C2Ext = C2.sext(FullWidth);
-    return (C1Ext + C2Ext).extractBits(C1.getBitWidth(), 1);
-  }
-  case ISD::AVGFLOORU: {
-    unsigned FullWidth = C1.getBitWidth() + 1;
-    APInt C1Ext = C1.zext(FullWidth);
-    APInt C2Ext = C2.zext(FullWidth);
-    return (C1Ext + C2Ext).extractBits(C1.getBitWidth(), 1);
-  }
-  case ISD::AVGCEILS: {
-    unsigned FullWidth = C1.getBitWidth() + 1;
-    APInt C1Ext = C1.sext(FullWidth);
-    APInt C2Ext = C2.sext(FullWidth);
-    return (C1Ext + C2Ext + 1).extractBits(C1.getBitWidth(), 1);
-  }
-  case ISD::AVGCEILU: {
-    unsigned FullWidth = C1.getBitWidth() + 1;
-    APInt C1Ext = C1.zext(FullWidth);
-    APInt C2Ext = C2.zext(FullWidth);
-    return (C1Ext + C2Ext + 1).extractBits(C1.getBitWidth(), 1);
-  }
+  case ISD::AVGFLOORS:
+    return APIntOps::avgFloorS(C1, C2);
+  case ISD::AVGFLOORU:
+    return APIntOps::avgFloorU(C1, C2);
+  case ISD::AVGCEILS:
+    return APIntOps::avgCeilS(C1, C2);
+  case ISD::AVGCEILU:
+    return APIntOps::avgCeilU(C1, C2);
   case ISD::ABDS:
     return APIntOps::smax(C1, C2) - APIntOps::smin(C1, C2);
   case ISD::ABDU:
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index e686b976523302..4c2188dbbbfb7f 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -3094,3 +3094,39 @@ void llvm::LoadIntFromMemory(APInt &IntVal, const uint8_t *Src,
     memcpy(Dst + sizeof(uint64_t) - LoadBytes, Src, LoadBytes);
   }
 }
+
+APInt APIntOps::avgFloorS(const APInt &C1, const APInt &C2) {
+
+  // Return floor((C1 + C2) /2))
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.sext(FullWidth);
+  APInt C2Ext = C2.sext(FullWidth);
+  return (C1Ext + C2Ext).extractBits(C1.getBitWidth(), 1);
+}
+
+APInt APIntOps::avgFloorU(const APInt &C1, const APInt &C2) {
+
+  // Return floor((C1 + C2) /2))
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.zext(FullWidth);
+  APInt C2Ext = C2.zext(FullWidth);
+  return (C1Ext + C2Ext).extractBits(C1.getBitWidth(), 1);
+}
+
+APInt APIntOps::avgCeilS(const APInt &C1, const APInt &C2) {
+
+  // Return ceil((C1 + C2) /2))
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.sext(FullWidth);
+  APInt C2Ext = C2.sext(FullWidth);
+  return (C1Ext + C2Ext + 1).extractBits(C1.getBitWidth(), 1);
+}
+
+APInt APIntOps::avgCeilU(const APInt &C1, const APInt &C2) {
+
+  // Return ceil((C1 + C2) /2))
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.zext(FullWidth);
+  APInt C2Ext = C2.zext(FullWidth);
+  return (C1Ext + C2Ext + 1).extractBits(C1.getBitWidth(), 1);
+}
\ No newline at end of file
diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 24324822356bf6..48beccb1f5167a 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -2877,6 +2877,56 @@ TEST(APIntTest, RoundingSDiv) {
   }
 }
 
+TEST(APIntTest, Average) {
+  APInt A2(32, 2);
+  APInt A100(32, 100);
+  APInt A101(32, 101);
+  APInt A200(32, 200, false);
+  APInt avg = APIntOps::avgFloorU(A100, A200);
+
+  EXPECT_EQ(APInt(32, 150), APIntOps::avgFloorU(A100, A200));
+  EXPECT_EQ(APIntOps::RoundingUDiv(A100 + A200, A2, APInt::Rounding::DOWN),
+            APIntOps::avgFloorU(A100, A200));
+  EXPECT_EQ(APIntOps::RoundingUDiv(A100 + A200, A2, APInt::Rounding::UP),
+            APIntOps::avgCeilU(A100, A200));
+  EXPECT_EQ(APIntOps::RoundingUDiv(A100 + A101, A2, APInt::Rounding::DOWN),
+            APIntOps::avgFloorU(A100, A101));
+  EXPECT_EQ(APIntOps::RoundingUDiv(A100 + A101, A2, APInt::Rounding::UP),
+            APIntOps::avgCeilU(A100, A101));
+
+  APInt Ap100(32, +100);
+  APInt Ap101(32, +101);
+  APInt Ap200(32, +200);
+  APInt Am100(32, -100);
+  APInt Am101(32, -101);
+  APInt Am200(32, -200);
+  EXPECT_EQ(APInt(32, +150), APIntOps::avgFloorS(Ap100, Ap200));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Ap100 + Ap200, A2, APInt::Rounding::DOWN),
+            APIntOps::avgFloorS(Ap100, Ap200));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Ap100 + Ap200, A2, APInt::Rounding::UP),
+            APIntOps::avgCeilS(Ap100, Ap200));
+
+  EXPECT_EQ(APInt(32, -150), APIntOps::avgFloorS(Am100, Am200));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Am100 + Am200, A2, APInt::Rounding::DOWN),
+            APIntOps::avgFloorS(Am100, Am200));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Am100 + Am200, A2, APInt::Rounding::UP),
+            APIntOps::avgCeilS(Am100, Am200));
+
+  EXPECT_EQ(APInt(32, +100), APIntOps::avgFloorS(Ap100, Ap101));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Ap100 + Ap101, A2, APInt::Rounding::DOWN),
+            APIntOps::avgFloorS(Ap100, Ap101));
+  EXPECT_EQ(APInt(32, +101), APIntOps::avgCeilS(Ap100, Ap101));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Ap100 + Ap101, A2, APInt::Rounding::UP),
+            APIntOps::avgCeilS(Ap100, Ap101));
+
+  EXPECT_EQ(APInt(32, -101), APIntOps::avgFloorS(Am100, Am101));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Am100 + Am101, A2, APInt::Rounding::DOWN),
+            APIntOps::avgFloorS(Am100, Am101));
+  EXPECT_EQ(APInt(32, -100), APIntOps::avgCeilS(Am100, Am101));
+  EXPECT_EQ(APIntOps::RoundingSDiv(Am100 + Am101, A2, APInt::Rounding::UP),
+            APIntOps::avgCeilS(Am100, Am101));
+}
+
 TEST(APIntTest, umul_ov) {
   const std::pair<uint64_t, uint64_t> Overflows[] = {
       {0x8000000000000000, 2},

RKSimon · 2024-03-08T09:51:52Z

llvm/lib/Support/APInt.cpp

@@ -3094,3 +3094,39 @@ void llvm::LoadIntFromMemory(APInt &IntVal, const uint8_t *Src,
    memcpy(Dst + sizeof(uint64_t) - LoadBytes, Src, LoadBytes);
  }
 }
+
+APInt APIntOps::avgFloorS(const APInt &C1, const APInt &C2) {
+


remove extra newlines

jayfoad · 2024-03-08T10:02:20Z

[ADT] Add implementations for avgFloor and ceilFloor to APInt

Typo "ceilFloor"

jayfoad · 2024-03-08T10:03:03Z

llvm/include/llvm/ADT/APInt.h

@@ -2193,6 +2193,18 @@ inline const APInt absdiff(const APInt &A, const APInt &B) {
  return A.uge(B) ? (A - B) : (B - A);
 }

+///.Compute the signed floor of the average of C1 and C2


Space instead of dot after ///

It is the average that is signed or unsigned, not the floor. So the comment should be "Compute the floor of the signed average of C1 and C2". Similarly for the others.

jayfoad · 2024-03-08T16:25:41Z

llvm/include/llvm/ADT/APInt.h

+/// Compute the floor of the signed average of C1 and C2
+APInt avgFloorS(const APInt &C1, const APInt &C2);
+
+/// Compute the floor of the average of C1 and C2


Should say "unsigned average" here for consistency. Same for avgCeilU below.

jayfoad · 2024-03-08T16:48:18Z

Incidentally Hacker's Delight has a section "Average of Two Integers" which has some neat tricks for implementing these operations without extending to N+1-bit integers.

RKSimon · 2024-03-08T16:58:58Z

Incidentally Hacker's Delight has a section "Average of Two Integers" which has some neat tricks for implementing these operations without extending to N+1-bit integers.

Thanks, we use min/max/sat/cmpsel instructions on TargetLowering::expandABD - using those as fallbacks might be a nice followup good-first-issue for someone :)

Atousa · 2024-03-08T18:23:51Z

@RKSimon @jayfoad Any further comments?

Atousa · 2024-03-08T18:28:23Z

Incidentally Hacker's Delight has a section "Average of Two Integers" which has some neat tricks for implementing these operations without extending to N+1-bit integers.

Thanks, we use min/max/sat/cmpsel instructions on TargetLowering::expandABD - using those as fallbacks might be a nice followup good-first-issue for someone :)

Can I open a new discussion regarding a better implementation of AvgFloor and AvgCeil in TargetLowering::expandABD?

llvm/lib/Support/APInt.cpp

RKSimon · 2024-03-09T16:47:48Z

Incidentally Hacker's Delight has a section "Average of Two Integers" which has some neat tricks for implementing these operations without extending to N+1-bit integers.

Thanks, we use min/max/sat/cmpsel instructions on TargetLowering::expandABD - using those as fallbacks might be a nice followup good-first-issue for someone :)

Can I open a new discussion regarding a better implementation of AvgFloor and AvgCeil in TargetLowering::expandABD?

I've raised a ticket here #84639

RKSimon · 2024-03-09T16:56:11Z

I've also raised #84640 for equivalent KnownBits handling

Atousa · 2024-03-11T04:00:37Z

humble ping @nikic @davemgreen @goldsteinn . Thanks!

llvm/unittests/ADT/APIntTest.cpp

topperc · 2024-03-11T05:57:29Z

llvm/lib/Support/APInt.cpp

@@ -3094,3 +3094,35 @@ void llvm::LoadIntFromMemory(APInt &IntVal, const uint8_t *Src,
    memcpy(Dst + sizeof(uint64_t) - LoadBytes, Src, LoadBytes);
  }
 }
+
+APInt APIntOps::avgFloorS(const APInt &C1, const APInt &C2) {
+  // Return floor((C1 + C2) /2))


/2 -> / 2

llvm/unittests/ADT/APIntTest.cpp

jayfoad · 2024-03-12T08:21:36Z

llvm/lib/Support/APInt.cpp

@@ -3094,3 +3094,35 @@ void llvm::LoadIntFromMemory(APInt &IntVal, const uint8_t *Src,
    memcpy(Dst + sizeof(uint64_t) - LoadBytes, Src, LoadBytes);
  }
 }
+
+APInt APIntOps::avgFloorS(const APInt &C1, const APInt &C2) {
+  // Return floor((C1 + C2)/2))


Suggested change

// Return floor((C1 + C2)/2))

// Return floor((C1 + C2)/2)

Similarly for the other comments below

RKSimon · 2024-03-12T09:10:33Z

llvm/lib/Support/APInt.cpp

+}
+
+APInt APIntOps::avgCeilU(const APInt &C1, const APInt &C2) {
+  // Return ceil((C1 + C2)/2))


Add assertions to all 4 methods that C1.getBitWidth() == C2.getBitWidth()

RKSimon · 2024-03-12T14:04:23Z

llvm/unittests/ADT/APIntTest.cpp

@@ -14,6 +14,7 @@
 #include "llvm/Support/Alignment.h"
 #include "gtest/gtest.h"
 #include <array>
+#include <limits.h>


#include <climits>

RKSimon

A couple of minors and a naming question - but other than that this almost looks ready

RKSimon · 2024-03-13T10:06:49Z

llvm/include/llvm/ADT/APInt.h

+APInt avgCeilS(const APInt &C1, const APInt &C2);
+
+/// Compute the ceil of the unsigned average of C1 and C2
+APInt avgCeilU(const APInt &C1, const APInt &C2);


Does anyone have any preference for camelcase vs lowercase?

RKSimon · 2024-03-13T10:07:41Z

llvm/lib/Support/APInt.cpp

+
+APInt APIntOps::avgFloorS(const APInt &C1, const APInt &C2) {
+  // Return floor((C1 + C2)/2)
+  assert(C1.getBitWidth() == C2.getBitWidth());


(style) Assertions must have messages (same below):

assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");

I know that's what the coding standards say, but it seems a bit silly when it encourages people to write a message that just says exactly the same as the condition, but in English.

Supports both signed and unsigned expansions. SelectionDAG now calls the APInt implementation of these functions.

Atousa · 2024-03-14T04:56:27Z

@jayfoad @RKSimon @kuhar @topperc @arsenm Thanks all for reviewing the PR!

RKSimon

LGTM - cheers

antmox · 2024-03-15T10:46:12Z

Hi, looks like this commit broke clang-arm64-windows-msvc-2stage bot:
https://lab.llvm.org/buildbot/#/builders/120/builds/6362

C:\Users\Tcwg\llvm-worker\clang-arm64-windows-msvc-2stage\llvm\llvm\unittests\ADT\APIntTest.cpp(2921,9): error: call to constructor of 'APInt' is ambiguous
 2921 |   APInt ApUMax(32, UINT_MAX, false);
      |         ^      ~~~~~~~~~~~~~~~~~~~
C:\Users\Tcwg\llvm-worker\clang-arm64-windows-msvc-2stage\llvm\llvm\include\llvm/ADT/APInt.h(109,3): note: candidate constructor
  109 |   APInt(unsigned numBits, uint64_t val, bool isSigned = false)
      |   ^
C:\Users\Tcwg\llvm-worker\clang-arm64-windows-msvc-2stage\llvm\llvm\include\llvm/ADT/APInt.h(135,3): note: candidate constructor
  135 |   APInt(unsigned numBits, unsigned numWords, const uint64_t bigVal[]);
      |   ^
1 error generated.

Could you please look at this ?

RKSimon · 2024-03-15T11:48:05Z

I've pushed a fix here 41bdcaa

Atousa marked this pull request as ready for review March 8, 2024 05:33

llvmbot added llvm:support llvm:SelectionDAG SelectionDAGISel as well llvm:adt labels Mar 8, 2024

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Atousa changed the title ~~[ADT] Add implementations for avgFloor and ceilFloor to APInt~~ [ADT] Add implementations for avgFloor and avgCeil to APInt Mar 8, 2024

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[DAG] TargetLowering::expandABD - investigate alternative expansions #84639

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[Support] Add KnownBits implementations for avgFloor and avgCeil #84640

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[ADT] Add implementations for avgFloor and avgCeil to APInt

362caa1

Supports both signed and unsigned expansions. SelectionDAG now calls the APInt implementation of these functions.

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[ADT] Add signed and unsigned mulh to APInt #84719

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[ADT] Add implementations for avgFloor and avgCeil to APInt #84431

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