Reland "[LTO] Run Argument Promotion before IPSCCP" (#111839)

Run ArgumentPromotion before IPSCCP in the LTO pipeline, to expose more
constants to be propagated. We also run PostOrderFunctionAttrs to
improve the information available to ArgumentPromotion's alias analysis,
and SROA to clean up allocas.

Author: hazzlim

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.
+    MPM.addPass(createModuleToPostOrderCGSCCPassAdaptor(
+        PostOrderFunctionAttrsPass(/*SkipNonRecursive*/ true)));
+    MPM.addPass(
+        createModuleToPostOrderCGSCCPassAdaptor(ArgumentPromotionPass()));
+    MPM.addPass(
+        createModuleToFunctionPassAdaptor(SROAPass(SROAOptions::ModifyCFG)));
+
     // 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.

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

@@ -41,14 +41,17 @@
 ; 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: AssumptionAnalysis on foo
-; 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-O23SZ-NEXT: Running pass: PostOrderFunctionAttrsPass
+; CHECK-O23SZ-NEXT: Running pass: ArgumentPromotionPass
+; CHECK-O23SZ-NEXT: Running pass: SROAPass
+; CHECK-O23SZ-NEXT: Running analysis: AssumptionAnalysis on foo
+; CHECK-O23SZ-NEXT: Running pass: IPSCCPPass
+; CHECK-O23SZ-NEXT: Running pass: CalledValuePropagationPass
 ; CHECK-O-NEXT: Running pass: PostOrderFunctionAttrsPass
 ; CHECK-O-NEXT: Running analysis: AAManager
 ; CHECK-O-NEXT: Running analysis: BasicAA

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

@@ -1,12 +1,12 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt -passes='lto<O3>' -S < %s | FileCheck %s
 
-; FIXME: We should be able to propagate the constants from @parent to @child.
+; 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]], i32 1024, i32 5)
+; CHECK-NEXT:    tail call fastcc void @child(ptr [[P]])
 ; CHECK-NEXT:    ret void
 ;
   %c = alloca i32
@@ -19,18 +19,18 @@ define void @parent(ptr %p) {
 
 define internal void @child(ptr %p, ptr %n, ptr %c) noinline {
 ; CHECK-LABEL: define internal fastcc void @child(
-; CHECK-SAME: ptr nocapture [[P:%.*]], i32 [[N_0_VAL:%.*]], i32 [[C_0_VAL:%.*]]) unnamed_addr #[[ATTR1:[0-9]+]] {
+; 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]], [[N_0_VAL]]
+; 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]], [[C_0_VAL]]
+; 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]]