[PATCH] D98145: [FastISel] Don't trivially kill extractvalues (PR49467)

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: probinson, craig.topper, spatel, RKSimon.
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All `extractvalue`s of the same value at the same index will map to the same register, so even if one specific extractvalue only has one use, we should not mark it as a trivial kill, as there may be more `extractvalue`s later.

Fixes https://bugs.llvm.org/show_bug.cgi?id=49467.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D98145

Files:
  llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
  llvm/test/CodeGen/X86/pr49467.ll


Index: llvm/test/CodeGen/X86/pr49467.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/pr49467.ll
@@ -0,0 +1,27 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -O0 -verify-machineinstrs -mtriple=x86_64 < %s | FileCheck %s
+
+declare { i8*, i64 } @get()
+
+declare void @use(i8*, i64)
+
+define void @test(i64* %p) nounwind {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    movq %rdi, (%rsp) # 8-byte Spill
+; CHECK-NEXT:    callq get at PLT
+; CHECK-NEXT:    movq (%rsp), %rdi # 8-byte Reload
+; CHECK-NEXT:    movq %rdx, %rsi
+; CHECK-NEXT:    movq %rsi, (%rdi)
+; CHECK-NEXT:    # implicit-def: $rdi
+; CHECK-NEXT:    callq use at PLT
+; CHECK-NEXT:    popq %rax
+; CHECK-NEXT:    retq
+  %struct = call { i8*, i64 } @get()
+  %struct.1 = extractvalue { i8*, i64 } %struct, 1
+  store i64 %struct.1, i64* %p, align 8
+  %struct.2 = extractvalue { i8*, i64 } %struct, 1
+  call void @use(i8* undef, i64 %struct.2)
+  ret void
+}
Index: llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -266,7 +266,8 @@
   return I->hasOneUse() &&
          !(I->getOpcode() == Instruction::BitCast ||
            I->getOpcode() == Instruction::PtrToInt ||
-           I->getOpcode() == Instruction::IntToPtr) &&
+           I->getOpcode() == Instruction::IntToPtr ||
+           I->getOpcode() == Instruction::ExtractValue) &&
          cast<Instruction>(*I->user_begin())->getParent() == I->getParent();
 }
 


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