Don't load values out of global constants with weak
linkage: the value may be replaced with something
different at link time. (Frontends that want to
allow values to be loaded out of weak constants can
give their constants weak_odr linkage).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67407 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 4a7f4c7..10671cd 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -11215,14 +11215,15 @@
// Instcombine load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
- if (GV->isConstant() && !GV->isDeclaration())
+ if (GV->isConstant() && !GV->isDeclaration() && !GV->mayBeOverridden())
return ReplaceInstUsesWith(LI, GV->getInitializer());
// Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
- if (GV->isConstant() && !GV->isDeclaration())
+ if (GV->isConstant() && !GV->isDeclaration() &&
+ !GV->mayBeOverridden())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return ReplaceInstUsesWith(LI, V);
@@ -11246,7 +11247,7 @@
// If this load comes from anywhere in a constant global, and if the global
// is all undef or zero, we know what it loads.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op->getUnderlyingObject())){
- if (GV->isConstant() && GV->hasInitializer()) {
+ if (GV->isConstant() && GV->hasInitializer() && !GV->mayBeOverridden()) {
if (GV->getInitializer()->isNullValue())
return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
else if (isa<UndefValue>(GV->getInitializer()))
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 7adc80f..a49bcc8 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1131,7 +1131,7 @@
// Transform load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
if (GV->isConstant()) {
- if (!GV->isDeclaration()) {
+ if (!GV->isDeclaration() && !GV->mayBeOverridden()) {
markConstant(IV, &I, GV->getInitializer());
return;
}
@@ -1150,7 +1150,7 @@
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::GetElementPtr)
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
- if (GV->isConstant() && !GV->isDeclaration())
+ if (GV->isConstant() && !GV->isDeclaration() && !GV->mayBeOverridden())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) {
markConstant(IV, &I, V);
diff --git a/lib/Transforms/Utils/CloneFunction.cpp b/lib/Transforms/Utils/CloneFunction.cpp
index 5921102..5dc2d1c 100644
--- a/lib/Transforms/Utils/CloneFunction.cpp
+++ b/lib/Transforms/Utils/CloneFunction.cpp
@@ -335,7 +335,8 @@
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
- if (GV->isConstant() && !GV->isDeclaration())
+ if (GV->isConstant() && !GV->isDeclaration() &&
+ !GV->mayBeOverridden())
return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
CE);
diff --git a/test/Feature/weak_constant.ll b/test/Feature/weak_constant.ll
new file mode 100644
index 0000000..d27adfe
--- /dev/null
+++ b/test/Feature/weak_constant.ll
@@ -0,0 +1,38 @@
+; RUN: llvm-as < %s | opt -std-compile-opts | llvm-dis > %t
+; RUN: grep undef %t | count 1
+; RUN: grep 5 %t | count 1
+; RUN: grep 7 %t | count 1
+; RUN: grep 9 %t | count 1
+
+ type { i32, i32 } ; type %0
+@a = weak constant i32 undef ; <i32*> [#uses=1]
+@b = weak constant i32 5 ; <i32*> [#uses=1]
+@c = weak constant %0 { i32 7, i32 9 } ; <%0*> [#uses=1]
+
+define i32 @la() {
+ %v = load i32* @a ; <i32> [#uses=1]
+ ret i32 %v
+}
+
+define i32 @lb() {
+ %v = load i32* @b ; <i32> [#uses=1]
+ ret i32 %v
+}
+
+define i32 @lc() {
+ %g = getelementptr %0* @c, i32 0, i32 0 ; <i32*> [#uses=1]
+ %u = load i32* %g ; <i32> [#uses=1]
+ %h = getelementptr %0* @c, i32 0, i32 1 ; <i32*> [#uses=1]
+ %v = load i32* %h ; <i32> [#uses=1]
+ %r = add i32 %u, %v
+ ret i32 %r
+}
+
+define i32 @f() {
+ %u = call i32 @la() ; <i32> [#uses=1]
+ %v = call i32 @lb() ; <i32> [#uses=1]
+ %w = call i32 @lc() ; <i32> [#uses=1]
+ %r = add i32 %u, %v ; <i32> [#uses=1]
+ %s = add i32 %r, %w ; <i32> [#uses=1]
+ ret i32 %s
+}
diff --git a/test/FrontendC/weak_constant.c b/test/FrontendC/weak_constant.c
new file mode 100644
index 0000000..5337948
--- /dev/null
+++ b/test/FrontendC/weak_constant.c
@@ -0,0 +1,12 @@
+// RUN: %llvmgcc -S %s -O1 -o - | grep {ret.*123}
+// Check for bug compatibility with gcc.
+
+const int x __attribute((weak)) = 123;
+
+int* f(void) {
+ return &x;
+}
+
+int g(void) {
+ return *f();
+}