[llvm] 6505b9d - Revert "[SimplifyCFG] Check if the return instruction causes undefined behavior"

[via llvm-commits]

Author: DianQK
Date: 2023-03-20T06:42:19+08:00
New Revision: 6505b9d049e5ec9f7620ec36d8e514f9e582199d

URL: https://github.com/llvm/llvm-project/commit/6505b9d049e5ec9f7620ec36d8e514f9e582199d
DIFF: https://github.com/llvm/llvm-project/commit/6505b9d049e5ec9f7620ec36d8e514f9e582199d.diff

LOG: Revert "[SimplifyCFG] Check if the return instruction causes undefined behavior"

This reverts commit b6a0be8ce3114d0c57e7a7d6c3c222986ca506ad.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Removed: 
    llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 9824cb3fb6ad..187f11a0a089 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -7115,20 +7115,6 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValu
         return passingValueIsAlwaysUndefined(V, GEP, PtrValueMayBeModified);
       }
 
-    // Look through return.
-    if (ReturnInst *Ret = dyn_cast<ReturnInst>(Use)) {
-      bool HasNoUndefAttr =
-          Ret->getFunction()->hasRetAttribute(Attribute::NoUndef);
-      // Return undefined to a noundef return value is undefined.
-      if (isa<UndefValue>(C) && HasNoUndefAttr)
-        return true;
-      // Return null to a nonnull+noundef return value is undefined.
-      if (C->isNullValue() && HasNoUndefAttr &&
-          Ret->getFunction()->hasRetAttribute(Attribute::NonNull)) {
-        return !PtrValueMayBeModified;
-      }
-    }
-
     // Look through bitcasts.
     if (BitCastInst *BC = dyn_cast<BitCastInst>(Use))
       return passingValueIsAlwaysUndefined(V, BC, PtrValueMayBeModified);

diff  --git a/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll b/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll
deleted file mode 100644
index e250a5d02c56..000000000000
--- a/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll
+++ /dev/null
@@ -1,122 +0,0 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S < %s | FileCheck %s
-
-define noundef i32 @test_ret_noundef(i1 %cond) {
-; CHECK-LABEL: @test_ret_noundef(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret i32 1
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %r = phi i32 [ undef, %entry ], [ 1, %bb1 ]
-  ret i32 %r
-}
-
-define i32 @test_ret(i1 %cond) {
-; CHECK-LABEL: @test_ret(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[COND:%.*]], i32 1, i32 undef
-; CHECK-NEXT:    ret i32 [[SPEC_SELECT]]
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %r = phi i32 [ undef, %entry ], [ 1, %bb1 ]
-  ret i32 %r
-}
-
-define nonnull noundef ptr @test_ret_ptr_nonnull_noundef(i1 %cond, ptr %x) {
-; CHECK-LABEL: @test_ret_ptr_nonnull_noundef(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    call void @llvm.assume(i1 [[COND:%.*]])
-; CHECK-NEXT:    ret ptr [[X:%.*]]
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %r = phi ptr [ null, %entry ], [ %x, %bb1 ]
-  ret ptr %r
-}
-
-define nonnull noundef ptr @test_ret_ptr_nonnull_noundef_gep_nonzero(i1 %cond, ptr %x) {
-; CHECK-LABEL: @test_ret_ptr_nonnull_noundef_gep_nonzero(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[COND:%.*]], ptr [[X:%.*]], ptr null
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds ptr, ptr [[SPEC_SELECT]], i64 12
-; CHECK-NEXT:    ret ptr [[GEP]]
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %phi = phi ptr [ null, %entry ], [ %x, %bb1 ]
-  %gep = getelementptr inbounds ptr, ptr %phi, i64 12
-  ret ptr %gep
-}
-
-define nonnull ptr @test_ret_ptr_nonnull(i1 %cond, ptr %x) {
-; CHECK-LABEL: @test_ret_ptr_nonnull(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[COND:%.*]], ptr [[X:%.*]], ptr null
-; CHECK-NEXT:    ret ptr [[SPEC_SELECT]]
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %r = phi ptr [ null, %entry ], [ %x, %bb1 ]
-  ret ptr %r
-}
-
-define noundef ptr @test_ret_ptr_noundef(i1 %cond, ptr %x) {
-; CHECK-LABEL: @test_ret_ptr_noundef(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[COND:%.*]], ptr [[X:%.*]], ptr null
-; CHECK-NEXT:    ret ptr [[SPEC_SELECT]]
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %r = phi ptr [ null, %entry ], [ %x, %bb1 ]
-  ret ptr %r
-}
-
-define ptr @test_ret_ptr(i1 %cond, ptr %x) {
-; CHECK-LABEL: @test_ret_ptr(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[SPEC_SELECT:%.*]] = select i1 [[COND:%.*]], ptr [[X:%.*]], ptr null
-; CHECK-NEXT:    ret ptr [[SPEC_SELECT]]
-;
-entry:
-  br i1 %cond, label %bb1, label %bb2
-
-bb1:
-  br label %bb2
-
-bb2:
-  %r = phi ptr [ null, %entry ], [ %x, %bb1 ]
-  ret ptr %r
-}