[llvm] [PowerPC] Alignment of toc-data symbol should not be increased during optimizations (PR #94593)
Kai Luo via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 17 17:49:49 PDT 2024
https://github.com/bzEq updated https://github.com/llvm/llvm-project/pull/94593
>From a499354b0dd9cc987fd9d0a9c6cd270e1a32bb66 Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Thu, 6 Jun 2024 09:07:13 +0000
Subject: [PATCH 1/8] Fix
---
llvm/lib/IR/Globals.cpp | 8 ++++++++
llvm/test/CodeGen/PowerPC/tocdata-firm-alignment.ll | 2 +-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 6f071847bb58a..2943a2aa0cf63 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -335,6 +335,14 @@ bool GlobalObject::canIncreaseAlignment() const {
if (isELF && !isDSOLocal())
return false;
+ bool isXCOFF =
+ (!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatXCOFF());
+ if (isXCOFF)
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
+ // GV with toc-data attribute is put in the region same as toc entry.
+ // Its alignment should be the same as toc entry.
+ return !GV->hasAttribute("toc-data");
+
return true;
}
diff --git a/llvm/test/CodeGen/PowerPC/tocdata-firm-alignment.ll b/llvm/test/CodeGen/PowerPC/tocdata-firm-alignment.ll
index c982713d4f8d3..4ecec36bc977a 100644
--- a/llvm/test/CodeGen/PowerPC/tocdata-firm-alignment.ll
+++ b/llvm/test/CodeGen/PowerPC/tocdata-firm-alignment.ll
@@ -5,7 +5,7 @@ target triple = "powerpc-ibm-aix7.2.0.0"
%struct.widget = type { i8, i8, i8 }
-; CHECK: @global = {{.*}}constant %struct.widget { i8 4, i8 0, i8 0 }, align 8 #0
+; CHECK: @global = {{.*}}constant %struct.widget { i8 4, i8 0, i8 0 }, align 4 #0
@global = constant %struct.widget { i8 4, i8 0, i8 0 }, align 4 #0
define void @baz() #1 {
>From 315e42bc7cfea8380a362dbb19b992d9ebd08fcd Mon Sep 17 00:00:00 2001
From: Kai Luo <gluokai at gmail.com>
Date: Thu, 6 Jun 2024 22:18:00 +0800
Subject: [PATCH 2/8] Adjust comment
Co-authored-by: Sean Fertile <sd.fertile at gmail.com>
---
llvm/lib/IR/Globals.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 2943a2aa0cf63..1d4116a9c4f9b 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -339,7 +339,8 @@ bool GlobalObject::canIncreaseAlignment() const {
(!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatXCOFF());
if (isXCOFF)
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
- // GV with toc-data attribute is put in the region same as toc entry.
+ // GV with toc-data attribute is defined in a TOC entry which
+ // has a fixed alignment and cannot be arbitrarily increased.
// Its alignment should be the same as toc entry.
return !GV->hasAttribute("toc-data");
>From f51b8d44b0b67dc4d6afe14ad75245d788bdcfa1 Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Thu, 6 Jun 2024 22:21:22 +0800
Subject: [PATCH 3/8] Adjust comment
---
llvm/lib/IR/Globals.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 1d4116a9c4f9b..9a91a324df732 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -341,7 +341,6 @@ bool GlobalObject::canIncreaseAlignment() const {
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
// GV with toc-data attribute is defined in a TOC entry which
// has a fixed alignment and cannot be arbitrarily increased.
- // Its alignment should be the same as toc entry.
return !GV->hasAttribute("toc-data");
return true;
>From 30aea5a91d2721a0832ed3f7fc0c28a4ebd4c804 Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Thu, 6 Jun 2024 22:24:55 +0800
Subject: [PATCH 4/8] Format
---
llvm/lib/IR/Globals.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 9a91a324df732..6a0536827f3ac 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -339,8 +339,8 @@ bool GlobalObject::canIncreaseAlignment() const {
(!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatXCOFF());
if (isXCOFF)
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
- // GV with toc-data attribute is defined in a TOC entry which
- // has a fixed alignment and cannot be arbitrarily increased.
+ // GV with toc-data attribute is defined in a TOC entry which has a fixed
+ // alignment and cannot be arbitrarily increased.
return !GV->hasAttribute("toc-data");
return true;
>From a935dc9a1c1cd2e2ef682f2fa11c49bc585cf00b Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Sat, 8 Jun 2024 09:52:44 +0800
Subject: [PATCH 5/8] Adjust comment
---
llvm/lib/IR/Globals.cpp | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 6a0536827f3ac..4d212e658d745 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -335,12 +335,13 @@ bool GlobalObject::canIncreaseAlignment() const {
if (isELF && !isDSOLocal())
return false;
+ // GV with toc-data attribute is defined in a TOC entry. To mitigate TOC
+ // overflow, the alignment of such symbol should not be increased. Otherwise,
+ // padding is needed thus more TOC entries are wasted.
bool isXCOFF =
(!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatXCOFF());
if (isXCOFF)
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
- // GV with toc-data attribute is defined in a TOC entry which has a fixed
- // alignment and cannot be arbitrarily increased.
return !GV->hasAttribute("toc-data");
return true;
>From 54621e10ddade2b30cc045f1ecb93c9451cf747c Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Sat, 8 Jun 2024 10:16:56 +0800
Subject: [PATCH 6/8] Add doc here
---
llvm/docs/LangRef.rst | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 9d7ade8eb523b..dde5ffc356b2a 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -812,6 +812,10 @@ doesn't). These kinds of structs (we may call them homogeneous scalable vector
structs) are considered sized and can be used in loads, stores, allocas, but
not GEPs.
+Globals with ``toc-data`` attribute set are stored in TOC of XCOFF. Their
+alignments are not larger than that of a TOC entry. Optimizations should not
+increase their alignments to prevent TOC overflow.
+
Syntax::
@<GlobalVarName> = [Linkage] [PreemptionSpecifier] [Visibility]
>From 6ac55a80ab5a5541d823715b5d80767f51862b9e Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Sat, 8 Jun 2024 10:18:50 +0800
Subject: [PATCH 7/8] Adjust wording
---
llvm/docs/LangRef.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index dde5ffc356b2a..8d2ce4d16aabf 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -814,7 +814,7 @@ not GEPs.
Globals with ``toc-data`` attribute set are stored in TOC of XCOFF. Their
alignments are not larger than that of a TOC entry. Optimizations should not
-increase their alignments to prevent TOC overflow.
+increase their alignments to mitigate TOC overflow.
Syntax::
>From 3dfc0edb4ed3da06980a602411132c036858710a Mon Sep 17 00:00:00 2001
From: Kai Luo <gluokai at gmail.com>
Date: Tue, 18 Jun 2024 08:49:39 +0800
Subject: [PATCH 8/8] Update llvm/lib/IR/Globals.cpp
Co-authored-by: Eli Friedman <efriedma at quicinc.com>
---
llvm/lib/IR/Globals.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 4d212e658d745..3cc29ea8a340d 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -342,7 +342,8 @@ bool GlobalObject::canIncreaseAlignment() const {
(!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatXCOFF());
if (isXCOFF)
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
- return !GV->hasAttribute("toc-data");
+ if (GV->hasAttribute("toc-data"))
+ return false;
return true;
}
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