[llvm] a58dcc5 - Reland "[SimplifyCFG] Improve the precision of `PtrValueMayBeModified`"
via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 24 14:42:54 PST 2024
Author: DianQK
Date: 2024-01-25T06:42:14+08:00
New Revision: a58dcc5e08665f2d58a28c9d4510cf94de6ed3bf
URL: https://github.com/llvm/llvm-project/commit/a58dcc5e08665f2d58a28c9d4510cf94de6ed3bf
DIFF: https://github.com/llvm/llvm-project/commit/a58dcc5e08665f2d58a28c9d4510cf94de6ed3bf.diff
LOG: Reland "[SimplifyCFG] Improve the precision of `PtrValueMayBeModified`"
This relands commit f890f010f6a70addbd885acd0c8d1b9578b6246f.
The result value of `getelementptr inbounds (TY, null, not zero)` is a poison value.
We can think of it as undefined behavior.
Added:
Modified:
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 97b3af518a27387..254795ec2445343 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -7395,7 +7395,16 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValu
// Look through GEPs. A load from a GEP derived from NULL is still undefined
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Use))
if (GEP->getPointerOperand() == I) {
- if (!GEP->isInBounds() || !GEP->hasAllZeroIndices())
+ // The current base address is null, there are four cases to consider:
+ // getelementptr (TY, null, 0) -> null
+ // getelementptr (TY, null, not zero) -> may be modified
+ // getelementptr inbounds (TY, null, 0) -> null
+ // getelementptr inbounds (TY, null, not zero) -> poison iff null is
+ // undefined?
+ if (!GEP->hasAllZeroIndices() &&
+ (!GEP->isInBounds() ||
+ NullPointerIsDefined(GEP->getFunction(),
+ GEP->getPointerAddressSpace())))
PtrValueMayBeModified = true;
return passingValueIsAlwaysUndefined(V, GEP, PtrValueMayBeModified);
}
diff --git a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
index 5ba43c055f9be12..757340527ec0303 100644
--- a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
+++ b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
@@ -444,6 +444,28 @@ else:
define void @test9_gep_inbounds_nonzero(i1 %X, ptr %Y) {
; CHECK-LABEL: @test9_gep_inbounds_nonzero(
; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = xor i1 [[X:%.*]], true
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP0]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr [[Y:%.*]], i64 12
+; CHECK-NEXT: [[TMP1:%.*]] = call ptr @fn_nonnull_noundef_arg(ptr [[GEP]])
+; CHECK-NEXT: ret void
+;
+entry:
+ br i1 %X, label %if, label %else
+
+if:
+ br label %else
+
+else:
+ %phi = phi ptr [ %Y, %entry ], [ null, %if ]
+ %gep = getelementptr inbounds i8, ptr %phi, i64 12
+ call ptr @fn_nonnull_noundef_arg(ptr %gep)
+ ret void
+}
+
+define void @test9_gep_inbounds_nonzero_null_defined(i1 %X, ptr %Y) #0 {
+; CHECK-LABEL: @test9_gep_inbounds_nonzero_null_defined(
+; CHECK-NEXT: entry:
; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[X:%.*]], ptr null, ptr [[Y:%.*]]
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr [[SPEC_SELECT]], i64 12
; CHECK-NEXT: [[TMP0:%.*]] = call ptr @fn_nonnull_noundef_arg(ptr [[GEP]])
@@ -462,9 +484,30 @@ else:
ret void
}
+define void @test9_gep_inbounds_unknown_null(i1 %X, ptr %Y, i64 %I) {
+; CHECK-LABEL: @test9_gep_inbounds_unknown_null(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = xor i1 [[X:%.*]], true
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP0]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr [[Y:%.*]], i64 [[I:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = call ptr @fn_nonnull_noundef_arg(ptr [[GEP]])
+; CHECK-NEXT: ret void
+;
+entry:
+ br i1 %X, label %if, label %else
+
+if:
+ br label %else
+
+else:
+ %phi = phi ptr [ %Y, %entry ], [ null, %if ]
+ %gep = getelementptr inbounds i8, ptr %phi, i64 %I
+ call ptr @fn_nonnull_noundef_arg(ptr %gep)
+ ret void
+}
-define void @test9_gep_inbouds_unknown_null(i1 %X, ptr %Y, i64 %I) {
-; CHECK-LABEL: @test9_gep_inbouds_unknown_null(
+define void @test9_gep_inbounds_unknown_null_defined(i1 %X, ptr %Y, i64 %I) #0 {
+; CHECK-LABEL: @test9_gep_inbounds_unknown_null_defined(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[X:%.*]], ptr null, ptr [[Y:%.*]]
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr [[SPEC_SELECT]], i64 [[I:%.*]]
@@ -484,6 +527,27 @@ else:
ret void
}
+define void @test9_gep_inbounds_unknown_null_call_noundef(i1 %X, ptr %Y, i64 %I) {
+; CHECK-LABEL: @test9_gep_inbounds_unknown_null_call_noundef(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[X:%.*]], ptr null, ptr [[Y:%.*]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr [[SPEC_SELECT]], i64 [[I:%.*]]
+; CHECK-NEXT: [[TMP0:%.*]] = call ptr @fn_noundef_arg(ptr [[GEP]])
+; CHECK-NEXT: ret void
+;
+entry:
+ br i1 %X, label %if, label %else
+
+if:
+ br label %else
+
+else:
+ %phi = phi ptr [ %Y, %entry ], [ null, %if ]
+ %gep = getelementptr inbounds i8, ptr %phi, i64 %I
+ call ptr @fn_noundef_arg(ptr %gep)
+ ret void
+}
+
define void @test9_gep_unknown_null(i1 %X, ptr %Y, i64 %I) {
; CHECK-LABEL: @test9_gep_unknown_null(
; CHECK-NEXT: entry:
diff --git a/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll b/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll
index e250a5d02c563c1..924f98a46ab541a 100644
--- a/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll
+++ b/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll
@@ -55,7 +55,26 @@ define nonnull noundef ptr @test_ret_ptr_nonnull_noundef_gep_nonzero(i1 %cond, p
; 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: [[GEP:%.*]] = getelementptr 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 ptr, ptr %phi, i64 12
+ ret ptr %gep
+}
+
+define nonnull noundef ptr @test_ret_ptr_nonnull_noundef_gep_inbounds_nonzero(i1 %cond, ptr %x) {
+; CHECK-LABEL: @test_ret_ptr_nonnull_noundef_gep_inbounds_nonzero(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: call void @llvm.assume(i1 [[COND:%.*]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds ptr, ptr [[X:%.*]], i64 12
; CHECK-NEXT: ret ptr [[GEP]]
;
entry:
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