Author: Stephen Tozer Date: 2025-02-25T11:57:01-08:00 New Revision: addf1c97117e52bd52f445a360047c2752df9d1a
URL: https://github.com/llvm/llvm-project/commit/addf1c97117e52bd52f445a360047c2752df9d1a DIFF: https://github.com/llvm/llvm-project/commit/addf1c97117e52bd52f445a360047c2752df9d1a.diff LOG: Do not treat llvm.fake.use as a debug instruction (#128684) The llvm.fake.use intrinsic is used to prevent certain values from being optimized out for the benefit of debug info; it is not, however, a debug or pseudo instruction itself and necessarily must not be treated as one, since its purpose is to act like a normal instruction. In the original commit that added them, the IR intrinsic however was treated as one in `getPrevNonDebugInstruction` (but _not_ in `getNextNonDebugInstruction`, or in the MIR equivalents). This patch correctly treats it as a non-debug instruction. (cherry picked from commit af68927a831c45b92248b1f6fc24d445be42dd91) Added: llvm/test/Transforms/SimplifyCFG/X86/fake-use-considered-when-sinking.ll Modified: llvm/lib/IR/Instruction.cpp Removed: ################################################################################ diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp index 84d9306ca6700..7d43de982df0d 100644 --- a/llvm/lib/IR/Instruction.cpp +++ b/llvm/lib/IR/Instruction.cpp @@ -1233,10 +1233,7 @@ Instruction::getNextNonDebugInstruction(bool SkipPseudoOp) const { const Instruction * Instruction::getPrevNonDebugInstruction(bool SkipPseudoOp) const { for (const Instruction *I = getPrevNode(); I; I = I->getPrevNode()) - if (!isa<DbgInfoIntrinsic>(I) && - !(SkipPseudoOp && isa<PseudoProbeInst>(I)) && - !(isa<IntrinsicInst>(I) && - cast<IntrinsicInst>(I)->getIntrinsicID() == Intrinsic::fake_use)) + if (!isa<DbgInfoIntrinsic>(I) && !(SkipPseudoOp && isa<PseudoProbeInst>(I))) return I; return nullptr; } diff --git a/llvm/test/Transforms/SimplifyCFG/X86/fake-use-considered-when-sinking.ll b/llvm/test/Transforms/SimplifyCFG/X86/fake-use-considered-when-sinking.ll new file mode 100644 index 0000000000000..63217315c978c --- /dev/null +++ b/llvm/test/Transforms/SimplifyCFG/X86/fake-use-considered-when-sinking.ll @@ -0,0 +1,67 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5 +; RUN: opt -p="simplifycfg<sink-common-insts>" -S < %s | FileCheck %s + +;; Verify that fake uses are not ignored when sinking instructions in +;; SimplifyCFG; when a fake use appears in only one incoming block they prevent +;; further sinking, and when identical fake uses appear on both sides they +;; are sunk normally. + +target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +define void @foo(i1 %bool, ptr %p) { +; CHECK-LABEL: define void @foo( +; CHECK-SAME: i1 [[BOOL:%.*]], ptr [[P:%.*]]) { +; CHECK-NEXT: [[ENTRY:.*:]] +; CHECK-NEXT: br i1 [[BOOL]], label %[[IF_ELSE:.*]], label %[[IF_THEN:.*]] +; CHECK: [[COMMON_RET:.*]]: +; CHECK-NEXT: ret void +; CHECK: [[IF_THEN]]: +; CHECK-NEXT: store ptr [[P]], ptr [[P]], align 8 +; CHECK-NEXT: br label %[[COMMON_RET]] +; CHECK: [[IF_ELSE]]: +; CHECK-NEXT: store ptr [[P]], ptr [[P]], align 8 +; CHECK-NEXT: notail call void (...) @llvm.fake.use(ptr [[P]]) +; CHECK-NEXT: br label %[[COMMON_RET]] +; +entry: + br i1 %bool, label %if.else, label %if.then + +common.ret: ; preds = %if.else, %if.then + ret void + +if.then: ; preds = %entry + store ptr %p, ptr %p, align 8 + br label %common.ret + +if.else: ; preds = %entry + store ptr %p, ptr %p, align 8 + notail call void (...) @llvm.fake.use(ptr %p) + br label %common.ret +} + +define void @bar(i1 %bool, ptr %p) { +; CHECK-LABEL: define void @bar( +; CHECK-SAME: i1 [[BOOL:%.*]], ptr [[P:%.*]]) { +; CHECK-NEXT: [[ENTRY:.*:]] +; CHECK-NEXT: store ptr [[P]], ptr [[P]], align 8 +; CHECK-NEXT: notail call void (...) @llvm.fake.use(ptr [[P]]) +; CHECK-NEXT: ret void +; +entry: + br i1 %bool, label %if.else, label %if.then + +common.ret: ; preds = %if.else, %if.then + ret void + +if.then: ; preds = %entry + store ptr %p, ptr %p, align 8 + notail call void (...) @llvm.fake.use(ptr %p) + br label %common.ret + +if.else: ; preds = %entry + store ptr %p, ptr %p, align 8 + notail call void (...) @llvm.fake.use(ptr %p) + br label %common.ret +} + _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
