[llvm] 38fc896 - [Attributor][Fix] Add alignment return attribute to HeapToStack

[Joseph Huber via llvm-commits]

Author: Joseph Huber
Date: 2021-12-27T16:58:23-05:00
New Revision: 38fc89623b3ea274ba45be20a19de217e45e1563

URL: https://github.com/llvm/llvm-project/commit/38fc89623b3ea274ba45be20a19de217e45e1563
DIFF: https://github.com/llvm/llvm-project/commit/38fc89623b3ea274ba45be20a19de217e45e1563.diff

LOG: [Attributor][Fix] Add alignment return attribute to HeapToStack

This patch changes the HeapToStack optimization to attach the return alignment
attribute information to the created alloca instruction. This would cause
problems when replacing the heap allocation with an alloca did not respect the
alignment of the original heap allocation, which would typically be aligned on
an 8 or 16 byte boundary. Malloc calls now contain alignment attributes,
so we can use that information here.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D115888

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/AttributorAttributes.cpp
    llvm/test/Transforms/Attributor/heap_to_stack.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index b977821bcaa68..468ae1c45c887 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -5929,6 +5929,8 @@ struct AAHeapToStackFunction final : public AAHeapToStack {
       }
 
       Align Alignment(1);
+      if (MaybeAlign RetAlign = AI.CB->getRetAlign())
+        Alignment = max(Alignment, RetAlign);
       if (AI.Kind == AllocationInfo::AllocationKind::ALIGNED_ALLOC) {
         Optional<APInt> AlignmentAPI =
             getAPInt(A, *this, *AI.CB->getArgOperand(0));

diff  --git a/llvm/test/Transforms/Attributor/heap_to_stack.ll b/llvm/test/Transforms/Attributor/heap_to_stack.ll
index 9979e0e1d9ca0..b9965b0d0f878 100644
--- a/llvm/test/Transforms/Attributor/heap_to_stack.ll
+++ b/llvm/test/Transforms/Attributor/heap_to_stack.ll
@@ -34,7 +34,7 @@ define void @h2s_value_simplify_interaction(i1 %c, i8* %A) {
 ; IS________OPM-LABEL: define {{[^@]+}}@h2s_value_simplify_interaction
 ; IS________OPM-SAME: (i1 [[C:%.*]], i8* nocapture nofree readnone [[A:%.*]]) {
 ; IS________OPM-NEXT:  entry:
-; IS________OPM-NEXT:    [[M:%.*]] = tail call noalias i8* @malloc(i64 noundef 4)
+; IS________OPM-NEXT:    [[M:%.*]] = tail call noalias align 16 i8* @malloc(i64 noundef 4)
 ; IS________OPM-NEXT:    br i1 [[C]], label [[T:%.*]], label [[F:%.*]]
 ; IS________OPM:       t:
 ; IS________OPM-NEXT:    br i1 false, label [[DEAD:%.*]], label [[F2:%.*]]
@@ -43,41 +43,41 @@ define void @h2s_value_simplify_interaction(i1 %c, i8* %A) {
 ; IS________OPM:       f2:
 ; IS________OPM-NEXT:    [[C1:%.*]] = bitcast i8* [[M]] to i32*
 ; IS________OPM-NEXT:    [[C2:%.*]] = bitcast i32* [[C1]] to i8*
-; IS________OPM-NEXT:    [[L:%.*]] = load i8, i8* [[C2]], align 1
+; IS________OPM-NEXT:    [[L:%.*]] = load i8, i8* [[C2]], align 16
 ; IS________OPM-NEXT:    call void @usei8(i8 [[L]])
-; IS________OPM-NEXT:    call void @no_sync_func(i8* nocapture nofree noundef [[C2]]) #[[ATTR5:[0-9]+]]
+; IS________OPM-NEXT:    call void @no_sync_func(i8* nocapture nofree noundef align 16 [[C2]]) #[[ATTR5:[0-9]+]]
 ; IS________OPM-NEXT:    br label [[J]]
 ; IS________OPM:       dead:
 ; IS________OPM-NEXT:    unreachable
 ; IS________OPM:       j:
 ; IS________OPM-NEXT:    [[PHI:%.*]] = phi i8* [ [[M]], [[F]] ], [ null, [[F2]] ]
-; IS________OPM-NEXT:    tail call void @no_sync_func(i8* nocapture nofree noundef [[PHI]]) #[[ATTR5]]
+; IS________OPM-NEXT:    tail call void @no_sync_func(i8* nocapture nofree noundef align 16 [[PHI]]) #[[ATTR5]]
 ; IS________OPM-NEXT:    ret void
 ;
 ; IS________NPM-LABEL: define {{[^@]+}}@h2s_value_simplify_interaction
 ; IS________NPM-SAME: (i1 [[C:%.*]], i8* nocapture nofree readnone [[A:%.*]]) {
 ; IS________NPM-NEXT:  entry:
-; IS________NPM-NEXT:    [[TMP0:%.*]] = alloca i8, i64 4, align 1
+; IS________NPM-NEXT:    [[TMP0:%.*]] = alloca i8, i64 4, align 16
 ; IS________NPM-NEXT:    br i1 [[C]], label [[T:%.*]], label [[F:%.*]]
 ; IS________NPM:       t:
 ; IS________NPM-NEXT:    br i1 false, label [[DEAD:%.*]], label [[F2:%.*]]
 ; IS________NPM:       f:
 ; IS________NPM-NEXT:    br label [[J:%.*]]
 ; IS________NPM:       f2:
-; IS________NPM-NEXT:    [[L:%.*]] = load i8, i8* [[TMP0]], align 1
+; IS________NPM-NEXT:    [[L:%.*]] = load i8, i8* [[TMP0]], align 16
 ; IS________NPM-NEXT:    call void @usei8(i8 [[L]])
-; IS________NPM-NEXT:    call void @no_sync_func(i8* nocapture nofree noundef [[TMP0]]) #[[ATTR6:[0-9]+]]
+; IS________NPM-NEXT:    call void @no_sync_func(i8* nocapture nofree noundef align 16 [[TMP0]]) #[[ATTR6:[0-9]+]]
 ; IS________NPM-NEXT:    br label [[J]]
 ; IS________NPM:       dead:
 ; IS________NPM-NEXT:    unreachable
 ; IS________NPM:       j:
 ; IS________NPM-NEXT:    [[PHI:%.*]] = phi i8* [ [[TMP0]], [[F]] ], [ null, [[F2]] ]
-; IS________NPM-NEXT:    tail call void @no_sync_func(i8* nocapture nofree noundef [[PHI]]) #[[ATTR6]]
+; IS________NPM-NEXT:    tail call void @no_sync_func(i8* nocapture nofree noundef align 16 [[PHI]]) #[[ATTR6]]
 ; IS________NPM-NEXT:    ret void
 ;
 entry:
   %add = add i64 2, 2
-  %m = tail call noalias i8* @malloc(i64 %add)
+  %m = tail call align 16 noalias i8* @malloc(i64 %add)
   br i1 %c, label %t, label %f
 t:
   br i1 false, label %dead, label %f2