[PATCH] D101228: [InlineCost] CallAnalyzer: use TTI info for extractvalue - they are free (PR50099)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added a reviewer: aeubanks.
lebedev.ri added a project: LLVM.
Herald added subscribers: steakhal, ASDenysPetrov, dkrupp, donat.nagy, Szelethus, a.sidorin, haicheng, baloghadamsoftware, hiraditya, eraman.
lebedev.ri requested review of this revision.

It seems incorrect to use TTI data in some places, and override it in others.
In this case, TTI says that `extractvalue` are free, yet we bill them.

While this doesn't address https://bugs.llvm.org/show_bug.cgi?id=50099 yet,
it reduces the cost from 55 to 50 while the threshold is 45.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101228

Files:
  llvm/lib/Analysis/InlineCost.cpp
  llvm/test/Transforms/Inline/X86/extractvalue.ll


Index: llvm/test/Transforms/Inline/X86/extractvalue.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Inline/X86/extractvalue.ll
@@ -0,0 +1,23 @@
+; RUN: opt < %s -inline -inline-threshold=0 -debug-only=inline-cost -print-instruction-comments -S -mtriple=x86_64-unknown-linux-gnu 2>&1 | FileCheck %s
+; RUN: opt < %s -passes='cgscc(inline)' -inline-threshold=0 -debug-only=inline-cost -print-instruction-comments -S -mtriple=x86_64-unknown-linux-gnu 2>&1 | FileCheck %s
+
+; REQUIRES: asserts
+
+; Check that extractvalue's are free.
+
+; CHECK-LABEL: define i32 @callee({ i32, i32 } %arg) {
+; CHECK-NEXT: ; cost before = -35, cost after = -35, threshold before = 0, threshold after = 0, cost delta = 0
+; CHECK-NEXT:   %r = extractvalue { i32, i32 } %arg, 0
+; CHECK-NEXT: ; cost before = -35, cost after = -35, threshold before = 0, threshold after = 0, cost delta = 0
+; CHECK-NEXT:   ret i32 %r
+; CHECK-NEXT: }
+
+define i32 @callee({i32, i32} %arg) {
+  %r = extractvalue {i32, i32} %arg, 0
+  ret i32 %r
+}
+
+define i32 @caller_range({i32, i32} %arg) {
+  %r = call i32 @callee({i32, i32} %arg)
+  ret i32 %r
+}
Index: llvm/lib/Analysis/InlineCost.cpp
===================================================================
--- llvm/lib/Analysis/InlineCost.cpp
+++ llvm/lib/Analysis/InlineCost.cpp
@@ -1769,6 +1769,11 @@
 }
 
 bool CallAnalyzer::visitExtractValue(ExtractValueInst &I) {
+  // Usually `extractvalue` is modelled as free.
+  if (TTI.getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) ==
+      TargetTransformInfo::TCC_Free)
+    return true;
+
   // Constant folding for extract value is trivial.
   if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
         return ConstantExpr::getExtractValue(COps[0], I.getIndices());


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