[CodeGen] TwoAddressInstructionPass: Control NumVisited limit via command line option

Pulled out of comment made on #80627 - to simplify further investigation into visit limits.

Since 10 was the limit over a decade ago, I have decided to increase it by 10-fold because that is around the number where compile time vs. benefit starts to wear off for the tests that changed codegen.

Author: AZero13

llvm/lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -80,6 +80,13 @@ EnableRescheduling("twoaddr-reschedule",
                    cl::desc("Coalesce copies by rescheduling (default=true)"),
                    cl::init(true), cl::Hidden);
 
+// Limit the number of rescheduling visits to dependent instructions.
+// FIXME: Arbitrary limit to reduce compile time cost.
+static cl::opt<unsigned>
+    MaxVisits("twoaddr-visit-limit", cl::Hidden, cl::init(100),
+              cl::desc("Maximum number of rescheduling visits to dependent "
+                       "instructions (0 = no limit)"));
+
 // Limit the number of dataflow edges to traverse when evaluating the benefit
 // of commuting operands.
 static cl::opt<unsigned> MaxDataFlowEdge(
@@ -994,7 +1001,7 @@ bool TwoAddressInstructionImpl::rescheduleMIBelowKill(
     // Debug or pseudo instructions cannot be counted against the limit.
     if (OtherMI.isDebugOrPseudoInstr())
       continue;
-    if (NumVisited > 10)  // FIXME: Arbitrary limit to reduce compile time cost.
+    if (MaxVisits && NumVisited > MaxVisits)
       return false;
     ++NumVisited;
     if (OtherMI.hasUnmodeledSideEffects() || OtherMI.isCall() ||
@@ -1160,14 +1167,14 @@ bool TwoAddressInstructionImpl::rescheduleKillAboveMI(
     }
   }
 
-  // Check if the reschedule will not break depedencies.
+  // Check if the reschedule will not break dependencies.
   unsigned NumVisited = 0;
   for (MachineInstr &OtherMI :
        make_range(mi, MachineBasicBlock::iterator(KillMI))) {
     // Debug or pseudo instructions cannot be counted against the limit.
     if (OtherMI.isDebugOrPseudoInstr())
       continue;
-    if (NumVisited > 10)  // FIXME: Arbitrary limit to reduce compile time cost.
+    if (MaxVisits && NumVisited > MaxVisits)
       return false;
     ++NumVisited;
     if (OtherMI.hasUnmodeledSideEffects() || OtherMI.isCall() ||

llvm/test/CodeGen/AArch64/sve-streaming-mode-fixed-length-int-extends.ll

@@ -1148,63 +1148,57 @@ define void @sext_v32i8_v32i64(ptr %in, ptr %out) {
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    ldp q1, q0, [x0]
 ; CHECK-NEXT:    add z0.b, z0.b, z0.b
-; CHECK-NEXT:    add z1.b, z1.b, z1.b
-; CHECK-NEXT:    mov z2.d, z0.d
-; CHECK-NEXT:    sunpklo z0.h, z0.b
-; CHECK-NEXT:    mov z3.d, z1.d
-; CHECK-NEXT:    sunpklo z1.h, z1.b
+; CHECK-NEXT:    add z2.b, z1.b, z1.b
+; CHECK-NEXT:    sunpklo z3.h, z0.b
+; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
+; CHECK-NEXT:    sunpklo z1.h, z2.b
 ; CHECK-NEXT:    ext z2.b, z2.b, z2.b, #8
+; CHECK-NEXT:    sunpklo z0.h, z0.b
+; CHECK-NEXT:    sunpklo z4.s, z3.h
 ; CHECK-NEXT:    ext z3.b, z3.b, z3.b, #8
-; CHECK-NEXT:    sunpklo z4.s, z0.h
-; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
 ; CHECK-NEXT:    sunpklo z5.s, z1.h
-; CHECK-NEXT:    ext z1.b, z1.b, z1.b, #8
 ; CHECK-NEXT:    sunpklo z2.h, z2.b
-; CHECK-NEXT:    sunpklo z3.h, z3.b
-; CHECK-NEXT:    sunpklo z0.s, z0.h
-; CHECK-NEXT:    sunpklo z16.d, z4.s
+; CHECK-NEXT:    ext z1.b, z1.b, z1.b, #8
+; CHECK-NEXT:    sunpklo z6.s, z0.h
+; CHECK-NEXT:    sunpklo z3.s, z3.h
+; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
+; CHECK-NEXT:    sunpklo z7.d, z4.s
 ; CHECK-NEXT:    ext z4.b, z4.b, z4.b, #8
-; CHECK-NEXT:    sunpklo z1.s, z1.h
-; CHECK-NEXT:    sunpklo z17.d, z5.s
+; CHECK-NEXT:    sunpklo z16.d, z5.s
 ; CHECK-NEXT:    ext z5.b, z5.b, z5.b, #8
-; CHECK-NEXT:    sunpklo z6.s, z2.h
-; CHECK-NEXT:    sunpklo z7.s, z3.h
+; CHECK-NEXT:    sunpklo z17.s, z2.h
 ; CHECK-NEXT:    ext z2.b, z2.b, z2.b, #8
-; CHECK-NEXT:    sunpklo z4.d, z4.s
+; CHECK-NEXT:    sunpklo z1.s, z1.h
+; CHECK-NEXT:    sunpklo z0.s, z0.h
+; CHECK-NEXT:    sunpklo z18.d, z6.s
+; CHECK-NEXT:    ext z6.b, z6.b, z6.b, #8
+; CHECK-NEXT:    sunpklo z19.d, z3.s
 ; CHECK-NEXT:    ext z3.b, z3.b, z3.b, #8
-; CHECK-NEXT:    sunpklo z19.d, z0.s
+; CHECK-NEXT:    sunpklo z4.d, z4.s
 ; CHECK-NEXT:    sunpklo z5.d, z5.s
-; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
 ; CHECK-NEXT:    sunpklo z2.s, z2.h
-; CHECK-NEXT:    sunpklo z18.d, z6.s
-; CHECK-NEXT:    ext z6.b, z6.b, z6.b, #8
-; CHECK-NEXT:    sunpklo z3.s, z3.h
-; CHECK-NEXT:    stp q16, q4, [x1, #128]
-; CHECK-NEXT:    mov z16.d, z7.d
-; CHECK-NEXT:    sunpklo z0.d, z0.s
-; CHECK-NEXT:    stp q17, q5, [x1]
-; CHECK-NEXT:    sunpklo z5.d, z7.s
-; CHECK-NEXT:    sunpklo z4.d, z6.s
-; CHECK-NEXT:    mov z6.d, z1.d
-; CHECK-NEXT:    ext z16.b, z16.b, z7.b, #8
-; CHECK-NEXT:    mov z7.d, z2.d
-; CHECK-NEXT:    stp q19, q0, [x1, #160]
-; CHECK-NEXT:    sunpklo z0.d, z2.s
-; CHECK-NEXT:    ext z6.b, z6.b, z1.b, #8
-; CHECK-NEXT:    sunpklo z1.d, z1.s
-; CHECK-NEXT:    stp q18, q4, [x1, #192]
-; CHECK-NEXT:    mov z4.d, z3.d
-; CHECK-NEXT:    ext z7.b, z7.b, z2.b, #8
-; CHECK-NEXT:    sunpklo z16.d, z16.s
 ; CHECK-NEXT:    sunpklo z6.d, z6.s
-; CHECK-NEXT:    ext z4.b, z4.b, z3.b, #8
-; CHECK-NEXT:    sunpklo z2.d, z7.s
 ; CHECK-NEXT:    sunpklo z3.d, z3.s
-; CHECK-NEXT:    stp q5, q16, [x1, #64]
-; CHECK-NEXT:    stp q1, q6, [x1, #32]
-; CHECK-NEXT:    sunpklo z1.d, z4.s
-; CHECK-NEXT:    stp q0, q2, [x1, #224]
-; CHECK-NEXT:    stp q3, q1, [x1, #96]
+; CHECK-NEXT:    stp q16, q5, [x1]
+; CHECK-NEXT:    sunpklo z5.d, z1.s
+; CHECK-NEXT:    ext z1.b, z1.b, z1.b, #8
+; CHECK-NEXT:    stp q7, q4, [x1, #128]
+; CHECK-NEXT:    sunpklo z4.d, z17.s
+; CHECK-NEXT:    ext z17.b, z17.b, z17.b, #8
+; CHECK-NEXT:    stp q18, q6, [x1, #192]
+; CHECK-NEXT:    sunpklo z6.d, z0.s
+; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
+; CHECK-NEXT:    stp q19, q3, [x1, #160]
+; CHECK-NEXT:    sunpklo z3.d, z2.s
+; CHECK-NEXT:    ext z2.b, z2.b, z2.b, #8
+; CHECK-NEXT:    sunpklo z7.d, z17.s
+; CHECK-NEXT:    sunpklo z1.d, z1.s
+; CHECK-NEXT:    sunpklo z0.d, z0.s
+; CHECK-NEXT:    sunpklo z2.d, z2.s
+; CHECK-NEXT:    stp q5, q1, [x1, #32]
+; CHECK-NEXT:    stp q4, q7, [x1, #64]
+; CHECK-NEXT:    stp q3, q2, [x1, #96]
+; CHECK-NEXT:    stp q6, q0, [x1, #224]
 ; CHECK-NEXT:    ret
 ;
 ; NONEON-NOSVE-LABEL: sext_v32i8_v32i64:
@@ -3133,63 +3127,57 @@ define void @zext_v32i8_v32i64(ptr %in, ptr %out) {
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    ldp q1, q0, [x0]
 ; CHECK-NEXT:    add z0.b, z0.b, z0.b
-; CHECK-NEXT:    add z1.b, z1.b, z1.b
-; CHECK-NEXT:    mov z2.d, z0.d
-; CHECK-NEXT:    uunpklo z0.h, z0.b
-; CHECK-NEXT:    mov z3.d, z1.d
-; CHECK-NEXT:    uunpklo z1.h, z1.b
+; CHECK-NEXT:    add z2.b, z1.b, z1.b
+; CHECK-NEXT:    uunpklo z3.h, z0.b
+; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
+; CHECK-NEXT:    uunpklo z1.h, z2.b
 ; CHECK-NEXT:    ext z2.b, z2.b, z2.b, #8
+; CHECK-NEXT:    uunpklo z0.h, z0.b
+; CHECK-NEXT:    uunpklo z4.s, z3.h
 ; CHECK-NEXT:    ext z3.b, z3.b, z3.b, #8
-; CHECK-NEXT:    uunpklo z4.s, z0.h
-; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
 ; CHECK-NEXT:    uunpklo z5.s, z1.h
-; CHECK-NEXT:    ext z1.b, z1.b, z1.b, #8
 ; CHECK-NEXT:    uunpklo z2.h, z2.b
-; CHECK-NEXT:    uunpklo z3.h, z3.b
-; CHECK-NEXT:    uunpklo z0.s, z0.h
-; CHECK-NEXT:    uunpklo z16.d, z4.s
+; CHECK-NEXT:    ext z1.b, z1.b, z1.b, #8
+; CHECK-NEXT:    uunpklo z6.s, z0.h
+; CHECK-NEXT:    uunpklo z3.s, z3.h
+; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
+; CHECK-NEXT:    uunpklo z7.d, z4.s
 ; CHECK-NEXT:    ext z4.b, z4.b, z4.b, #8
-; CHECK-NEXT:    uunpklo z1.s, z1.h
-; CHECK-NEXT:    uunpklo z17.d, z5.s
+; CHECK-NEXT:    uunpklo z16.d, z5.s
 ; CHECK-NEXT:    ext z5.b, z5.b, z5.b, #8
-; CHECK-NEXT:    uunpklo z6.s, z2.h
-; CHECK-NEXT:    uunpklo z7.s, z3.h
+; CHECK-NEXT:    uunpklo z17.s, z2.h
 ; CHECK-NEXT:    ext z2.b, z2.b, z2.b, #8
-; CHECK-NEXT:    uunpklo z4.d, z4.s
+; CHECK-NEXT:    uunpklo z1.s, z1.h
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpklo z18.d, z6.s
+; CHECK-NEXT:    ext z6.b, z6.b, z6.b, #8
+; CHECK-NEXT:    uunpklo z19.d, z3.s
 ; CHECK-NEXT:    ext z3.b, z3.b, z3.b, #8
-; CHECK-NEXT:    uunpklo z19.d, z0.s
+; CHECK-NEXT:    uunpklo z4.d, z4.s
 ; CHECK-NEXT:    uunpklo z5.d, z5.s
-; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
 ; CHECK-NEXT:    uunpklo z2.s, z2.h
-; CHECK-NEXT:    uunpklo z18.d, z6.s
-; CHECK-NEXT:    ext z6.b, z6.b, z6.b, #8
-; CHECK-NEXT:    uunpklo z3.s, z3.h
-; CHECK-NEXT:    stp q16, q4, [x1, #128]
-; CHECK-NEXT:    mov z16.d, z7.d
-; CHECK-NEXT:    uunpklo z0.d, z0.s
-; CHECK-NEXT:    stp q17, q5, [x1]
-; CHECK-NEXT:    uunpklo z5.d, z7.s
-; CHECK-NEXT:    uunpklo z4.d, z6.s
-; CHECK-NEXT:    mov z6.d, z1.d
-; CHECK-NEXT:    ext z16.b, z16.b, z7.b, #8
-; CHECK-NEXT:    mov z7.d, z2.d
-; CHECK-NEXT:    stp q19, q0, [x1, #160]
-; CHECK-NEXT:    uunpklo z0.d, z2.s
-; CHECK-NEXT:    ext z6.b, z6.b, z1.b, #8
-; CHECK-NEXT:    uunpklo z1.d, z1.s
-; CHECK-NEXT:    stp q18, q4, [x1, #192]
-; CHECK-NEXT:    mov z4.d, z3.d
-; CHECK-NEXT:    ext z7.b, z7.b, z2.b, #8
-; CHECK-NEXT:    uunpklo z16.d, z16.s
 ; CHECK-NEXT:    uunpklo z6.d, z6.s
-; CHECK-NEXT:    ext z4.b, z4.b, z3.b, #8
-; CHECK-NEXT:    uunpklo z2.d, z7.s
 ; CHECK-NEXT:    uunpklo z3.d, z3.s
-; CHECK-NEXT:    stp q5, q16, [x1, #64]
-; CHECK-NEXT:    stp q1, q6, [x1, #32]
-; CHECK-NEXT:    uunpklo z1.d, z4.s
-; CHECK-NEXT:    stp q0, q2, [x1, #224]
-; CHECK-NEXT:    stp q3, q1, [x1, #96]
+; CHECK-NEXT:    stp q16, q5, [x1]
+; CHECK-NEXT:    uunpklo z5.d, z1.s
+; CHECK-NEXT:    ext z1.b, z1.b, z1.b, #8
+; CHECK-NEXT:    stp q7, q4, [x1, #128]
+; CHECK-NEXT:    uunpklo z4.d, z17.s
+; CHECK-NEXT:    ext z17.b, z17.b, z17.b, #8
+; CHECK-NEXT:    stp q18, q6, [x1, #192]
+; CHECK-NEXT:    uunpklo z6.d, z0.s
+; CHECK-NEXT:    ext z0.b, z0.b, z0.b, #8
+; CHECK-NEXT:    stp q19, q3, [x1, #160]
+; CHECK-NEXT:    uunpklo z3.d, z2.s
+; CHECK-NEXT:    ext z2.b, z2.b, z2.b, #8
+; CHECK-NEXT:    uunpklo z7.d, z17.s
+; CHECK-NEXT:    uunpklo z1.d, z1.s
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    uunpklo z2.d, z2.s
+; CHECK-NEXT:    stp q5, q1, [x1, #32]
+; CHECK-NEXT:    stp q4, q7, [x1, #64]
+; CHECK-NEXT:    stp q3, q2, [x1, #96]
+; CHECK-NEXT:    stp q6, q0, [x1, #224]
 ; CHECK-NEXT:    ret
 ;
 ; NONEON-NOSVE-LABEL: zext_v32i8_v32i64: