[llvm] [GlobalOpt] Fix global SRA incorrect alignment on some elements (PR #115328)
Bruno De Fraine via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 7 13:58:36 PST 2024
https://github.com/brunodf-snps updated https://github.com/llvm/llvm-project/pull/115328
>From 2d1cd65a3237f31a74181413aa50c5821de69f48 Mon Sep 17 00:00:00 2001
From: Bruno De Fraine <brunodf at synopsys.com>
Date: Thu, 7 Nov 2024 15:49:38 +0100
Subject: [PATCH 1/2] [GlobalOpt] Fix global SRA incorrect use of original
alignment on some elements
The logic had a flaw where the alignment from the original aggregate is
unintentionally retained when the calculated known alignment is not
higher than the ABI type alignment.
Fixes #115282
---
llvm/lib/Transforms/IPO/GlobalOpt.cpp | 7 ++++---
llvm/test/DebugInfo/X86/global-sra-struct-fit-segment.ll | 2 +-
.../X86/global-sra-struct-part-overlap-segment.ll | 2 +-
llvm/test/Transforms/GlobalOpt/globalsra-align.ll | 8 ++++----
4 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 4647c65a5c850f..9aaa0212fc8445 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -575,15 +575,16 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
*GV->getParent(), Ty, false, GlobalVariable::InternalLinkage,
Initializer, GV->getName() + "." + Twine(NameSuffix++), GV,
GV->getThreadLocalMode(), GV->getAddressSpace());
+ // Start out by copying attributes from the original, including alignment.
NGV->copyAttributesFrom(GV);
NewGlobals.insert({OffsetForTy, NGV});
// Calculate the known alignment of the field. If the original aggregate
- // had 256 byte alignment for example, something might depend on that:
+ // had 256 byte alignment for example, then the element at a given offset
+ // may also have a known alignment, and something might depend on that:
// propagate info to each field.
Align NewAlign = commonAlignment(StartAlignment, OffsetForTy);
- if (NewAlign > DL.getABITypeAlign(Ty))
- NGV->setAlignment(NewAlign);
+ NGV->setAlignment(std::max(NewAlign, DL.getABITypeAlign(Ty)));
// Copy over the debug info for the variable.
transferSRADebugInfo(GV, NGV, OffsetForTy * 8,
diff --git a/llvm/test/DebugInfo/X86/global-sra-struct-fit-segment.ll b/llvm/test/DebugInfo/X86/global-sra-struct-fit-segment.ll
index 94b7deec95f411..ab48ef2411f35c 100644
--- a/llvm/test/DebugInfo/X86/global-sra-struct-fit-segment.ll
+++ b/llvm/test/DebugInfo/X86/global-sra-struct-fit-segment.ll
@@ -20,7 +20,7 @@
%struct.BSS1 = type <{ [12 x i8] }>
;CHECK: @.BSS1.0 = internal unnamed_addr global i32 0, align 32, !dbg ![[GVE1:.*]]
-;CHECK: @.BSS1.1 = internal unnamed_addr global i32 0, align 32, !dbg ![[GVE2:.*]], !dbg ![[GVE4:.*]]
+;CHECK: @.BSS1.1 = internal unnamed_addr global i32 0, align 4, !dbg ![[GVE2:.*]], !dbg ![[GVE4:.*]]
;CHECK: @.BSS1.2 = internal unnamed_addr global i32 0, align 8, !dbg ![[GVE3:.*]]
@.BSS1 = internal global %struct.BSS1 zeroinitializer, align 32, !dbg !0, !dbg !7, !dbg !10, !dbg !27, !dbg !29
diff --git a/llvm/test/DebugInfo/X86/global-sra-struct-part-overlap-segment.ll b/llvm/test/DebugInfo/X86/global-sra-struct-part-overlap-segment.ll
index d7854cb822e3e9..9dd865edbbdadd 100644
--- a/llvm/test/DebugInfo/X86/global-sra-struct-part-overlap-segment.ll
+++ b/llvm/test/DebugInfo/X86/global-sra-struct-part-overlap-segment.ll
@@ -26,7 +26,7 @@
@.BSS3 = internal unnamed_addr global %struct.BSS3 zeroinitializer, align 32, !dbg !0, !dbg !7, !dbg !29
;CHECK: @.BSS3.0 = internal unnamed_addr global double 0.000000e+00, align 32, !dbg ![[GVE1:.*]], !dbg ![[GVE2:.*]]
-;CHECK: @.BSS3.1 = internal unnamed_addr global double 0.000000e+00, align 32, !dbg ![[GVE3:.*]], !dbg ![[GVE4:.*]], !dbg ![[GVE6:.*]]
+;CHECK: @.BSS3.1 = internal unnamed_addr global double 0.000000e+00, align 8, !dbg ![[GVE3:.*]], !dbg ![[GVE4:.*]], !dbg ![[GVE6:.*]]
;CHECK: @.BSS3.2 = internal unnamed_addr global double 0.000000e+00, align 16, !dbg ![[GVE5:.*]]
@.C363_mymod_bar_ = internal constant [2 x i8] c"IF"
diff --git a/llvm/test/Transforms/GlobalOpt/globalsra-align.ll b/llvm/test/Transforms/GlobalOpt/globalsra-align.ll
index aadd5b866a8224..74ccb3f279ed09 100644
--- a/llvm/test/Transforms/GlobalOpt/globalsra-align.ll
+++ b/llvm/test/Transforms/GlobalOpt/globalsra-align.ll
@@ -15,9 +15,9 @@ target datalayout = "p:16:32:64" ; 16-bit pointers with 32-bit ABI alignment and
;.
; CHECK: @[[A_4:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 8
-; CHECK: @[[A_5:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 16
+; CHECK: @[[A_5:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 8
; CHECK: @[[A_6:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 16
-; CHECK: @[[A_7:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 16
+; CHECK: @[[A_7:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 8
;.
define ptr @reduce_align_0() {
; CHECK-LABEL: @reduce_align_0(
@@ -31,7 +31,7 @@ define ptr @reduce_align_0() {
define ptr @reduce_align_1() {
; CHECK-LABEL: @reduce_align_1(
-; CHECK-NEXT: [[X:%.*]] = load ptr, ptr @a.5, align 16
+; CHECK-NEXT: [[X:%.*]] = load ptr, ptr @a.5, align 8
; CHECK-NEXT: ret ptr [[X]]
;
%x = load ptr, ptr getelementptr inbounds ([3 x [7 x ptr]], ptr @a, i64 0, i64 2, i64 1), align 4
@@ -51,7 +51,7 @@ define ptr @reduce_align_2() {
define ptr @reduce_align_3() {
; CHECK-LABEL: @reduce_align_3(
-; CHECK-NEXT: [[X:%.*]] = load ptr, ptr @a.7, align 16
+; CHECK-NEXT: [[X:%.*]] = load ptr, ptr @a.7, align 8
; CHECK-NEXT: ret ptr [[X]]
;
%x = load ptr, ptr getelementptr inbounds ([3 x [7 x ptr]], ptr @a, i64 0, i64 2, i64 3), align 4
>From f5151ec2cdf70e7ccb7975a69010edef0479a497 Mon Sep 17 00:00:00 2001
From: Bruno De Fraine <brunodf at synopsys.com>
Date: Thu, 7 Nov 2024 22:56:44 +0100
Subject: [PATCH 2/2] Checking for ABI type align is unnecessary
---
llvm/lib/Transforms/IPO/GlobalOpt.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 9aaa0212fc8445..3381b5f77683b5 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -584,7 +584,7 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
// may also have a known alignment, and something might depend on that:
// propagate info to each field.
Align NewAlign = commonAlignment(StartAlignment, OffsetForTy);
- NGV->setAlignment(std::max(NewAlign, DL.getABITypeAlign(Ty)));
+ NGV->setAlignment(NewAlign);
// Copy over the debug info for the variable.
transferSRADebugInfo(GV, NGV, OffsetForTy * 8,
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