Reland "[LTO] Run Argument Promotion before IPSCCP"

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -1828,6 +1828,15 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
     MPM.addPass(PGOIndirectCallPromotion(
         true /* InLTO */, PGOOpt && PGOOpt->Action == PGOOptions::SampleUse));
 
+    // Promoting by-reference arguments to by-value exposes more constants to
+    // IPSCCP.
+    CGSCCPassManager CGPM;
+    CGPM.addPass(PostOrderFunctionAttrsPass());
+    CGPM.addPass(ArgumentPromotionPass());
+    CGPM.addPass(
+        createCGSCCToFunctionPassAdaptor(SROAPass(SROAOptions::ModifyCFG)));
+    MPM.addPass(createModuleToPostOrderCGSCCPassAdaptor(std::move(CGPM)));
+
     // Propagate constants at call sites into the functions they call.  This
     // opens opportunities for globalopt (and inlining) by substituting function
     // pointers passed as arguments to direct uses of functions.
@@ -1840,10 +1849,6 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
     MPM.addPass(CalledValuePropagationPass());
   }
 
-  // Now deduce any function attributes based in the current code.
-  MPM.addPass(
-      createModuleToPostOrderCGSCCPassAdaptor(PostOrderFunctionAttrsPass()));
-
   // Do RPO function attribute inference across the module to forward-propagate
   // attributes where applicable.
   // FIXME: Is this really an optimization rather than a canonicalization?

llvm/test/Other/new-pm-lto-defaults.ll

@@ -41,24 +41,24 @@
 ; CHECK-O23SZ-NEXT: PGOIndirectCallPromotion
 ; CHECK-O23SZ-NEXT: Running analysis: ProfileSummaryAnalysis
 ; CHECK-O23SZ-NEXT: Running analysis: OptimizationRemarkEmitterAnalysis
-; CHECK-O23SZ-NEXT: Running pass: IPSCCPPass
+; CHECK-O23SZ-NEXT: Running analysis: InnerAnalysisManagerProxy<{{.*}}SCC
+; CHECK-O23SZ-NEXT: Running analysis: LazyCallGraphAnalysis
+; CHECK-O23SZ-NEXT: Running analysis: FunctionAnalysisManagerCGSCCProxy
+; CHECK-O23SZ-NEXT: Running analysis: OuterAnalysisManagerProxy<{{.*}}LazyCallGraph{{.*}}>
+; CHECK-O23SZ-NEXT: Running pass: PostOrderFunctionAttrsPass
+; CHECK-O23SZ-NEXT: Running analysis: AAManager
+; CHECK-O23SZ-NEXT: Running analysis: BasicAA
 ; CHECK-O23SZ-NEXT: Running analysis: AssumptionAnalysis on foo
+; CHECK-O23SZ-NEXT: Running analysis: ScopedNoAliasAA
+; CHECK-O23SZ-NEXT: Running analysis: TypeBasedAA
+; CHECK-O23SZ-NEXT: Running analysis: OuterAnalysisManagerProxy
+; CHECK-O23SZ-NEXT: Running pass: ArgumentPromotionPass
+; CHECK-O23SZ-NEXT: Running pass: SROAPass
+; CHECK-O23SZ-NEXT: Running pass: IPSCCPPass
 ; CHECK-O23SZ-NEXT: Running pass: CalledValuePropagationPass
-; CHECK-O-NEXT: Running analysis: InnerAnalysisManagerProxy<{{.*}}SCC
-; CHECK-O-NEXT: Running analysis: LazyCallGraphAnalysis
-; CHECK-O1-NEXT: Running analysis: TargetLibraryAnalysis
-; CHECK-O-NEXT: Running analysis: FunctionAnalysisManagerCGSCCProxy
-; CHECK-O-NEXT: Running analysis: OuterAnalysisManagerProxy<{{.*}}LazyCallGraph{{.*}}>
-; CHECK-O-NEXT: Running pass: PostOrderFunctionAttrsPass
-; CHECK-O-NEXT: Running analysis: AAManager
-; CHECK-O-NEXT: Running analysis: BasicAA
-; CHECK-O1-NEXT: Running analysis: AssumptionAnalysis on foo
-; CHECK-O1-NEXT: Running analysis: TargetIRAnalysis
-; CHECK-O1-NEXT: Running analysis: DominatorTreeAnalysis
-; CHECK-O-NEXT: Running analysis: ScopedNoAliasAA
-; CHECK-O-NEXT: Running analysis: TypeBasedAA
-; CHECK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
 ; CHECK-O-NEXT: Running pass: ReversePostOrderFunctionAttrsPass
+; CHECK-O1-NEXT: Running analysis: LazyCallGraphAnalysis
+; CHECK-O1-NEXT: Running analysis: TargetLibraryAnalysis
 ; CHECK-O-NEXT: Running pass: GlobalSplitPass
 ; CHECK-O-NEXT: Running pass: WholeProgramDevirtPass
 ; CHECK-O1-NEXT: Running pass: LowerTypeTestsPass

llvm/test/Transforms/PhaseOrdering/lto-argpromotion-ipsccp.ll

@@ -0,0 +1,68 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes='lto<O3>' -S < %s | FileCheck %s
+
+; We should be able to propagate the constants from @parent to @child.
+
+define void @parent(ptr %p) {
+; CHECK-LABEL: define void @parent(
+; CHECK-SAME: ptr nocapture [[P:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    tail call fastcc void @child(ptr [[P]])
+; CHECK-NEXT:    ret void
+;
+  %c = alloca i32
+  store i32 5, ptr %c
+  %n = alloca i32
+  store i32 1024, ptr %n
+  call void @child(ptr %p, ptr %n, ptr %c)
+  ret void
+}
+
+define internal void @child(ptr %p, ptr %n, ptr %c) noinline {
+; CHECK-LABEL: define internal fastcc void @child(
+; CHECK-SAME: ptr nocapture [[P:%.*]]) unnamed_addr #[[ATTR1:[0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    br label %[[FOR_COND:.*]]
+; CHECK:       [[FOR_COND]]:
+; CHECK-NEXT:    [[I_0:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[INC:%.*]], %[[FOR_INC:.*]] ]
+; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[I_0]], 1024
+; CHECK-NEXT:    br i1 [[CMP_NOT]], label %[[FOR_END:.*]], label %[[FOR_INC]]
+; CHECK:       [[FOR_INC]]:
+; CHECK-NEXT:    [[IDXPROM:%.*]] = zext nneg i32 [[I_0]] to i64
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 [[IDXPROM]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[TMP0]], 5
+; CHECK-NEXT:    store i32 [[MUL]], ptr [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I_0]], 1
+; CHECK-NEXT:    br label %[[FOR_COND]]
+; CHECK:       [[FOR_END]]:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.cond
+
+for.cond:
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+  %n.val = load i32, ptr %n
+  %cmp = icmp ne i32 %i.0, %n.val
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+  br label %for.end
+
+for.body:
+  %idxprom = sext i32 %i.0 to i64
+  %arrayidx = getelementptr inbounds i32, ptr %p, i64 %idxprom
+  %0 = load i32, ptr %arrayidx, align 4
+  %c.val = load i32, ptr %c
+  %mul = mul i32 %0, %c.val
+  store i32 %mul, ptr %arrayidx, align 4
+  br label %for.inc
+
+for.inc:
+  %inc = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end:
+  ret void
+}
+