[llvm] d751f86 - [ConstantFold] Make areGlobalsPotentiallyEqual less aggressive.

[Eli Friedman via llvm-commits]

Author: Eli Friedman
Date: 2020-09-11T17:23:08-07:00
New Revision: d751f86189a7f7ef2a6fe06974a5da3349b02f20

URL: https://github.com/llvm/llvm-project/commit/d751f86189a7f7ef2a6fe06974a5da3349b02f20
DIFF: https://github.com/llvm/llvm-project/commit/d751f86189a7f7ef2a6fe06974a5da3349b02f20.diff

LOG: [ConstantFold] Make areGlobalsPotentiallyEqual less aggressive.

In particular, we shouldn't make assumptions about globals which are
unnamed_addr: we can fold them together with other globals.

Also while I'm here, use isInterposable() instead of trying to
explicitly name all the different kinds of weak linkage.

Fixes https://bugs.llvm.org/show_bug.cgi?id=47090

Differential Revision: https://reviews.llvm.org/D87123

Added: 
    

Modified: 
    llvm/lib/IR/ConstantFold.cpp
    llvm/test/Assembler/ConstantExprNoFold.ll
    llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index a827d9144c07..3f00dd057536 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -1616,7 +1616,7 @@ static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
 static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
                                                       const GlobalValue *GV2) {
   auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
-    if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage())
+    if (GV->isInterposable() || GV->hasGlobalUnnamedAddr())
       return true;
     if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
       Type *Ty = GVar->getValueType();

diff  --git a/llvm/test/Assembler/ConstantExprNoFold.ll b/llvm/test/Assembler/ConstantExprNoFold.ll
index 42e558eb3865..d91855925c89 100644
--- a/llvm/test/Assembler/ConstantExprNoFold.ll
+++ b/llvm/test/Assembler/ConstantExprNoFold.ll
@@ -42,6 +42,12 @@ target datalayout = "p:32:32"
 @empty.2 = external global [0 x i8], align 1
 @empty.cmp = global i1 icmp eq ([0 x i8]* @empty.1, [0 x i8]* @empty.2)
 
+; Two unnamed_addr globals can share an address
+; CHECK: @unnamed.cmp = global i1 icmp eq ([5 x i8]* @unnamed.1, [5 x i8]* @unnamed.2)
+ at unnamed.1 = unnamed_addr constant [5 x i8] c"asdf\00"
+ at unnamed.2 = unnamed_addr constant [5 x i8] c"asdf\00"
+ at unnamed.cmp = global i1 icmp eq ([5 x i8]* @unnamed.1, [5 x i8]* @unnamed.2)
+
 @addrspace3 = internal addrspace(3) global i32 undef
 
 ; CHECK: @no.fold.addrspace.icmp.eq.gv.null = global i1 icmp eq (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)

diff  --git a/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll b/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
index ad0fe5a21783..da9d0469e5e2 100644
--- a/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
+++ b/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
@@ -16,8 +16,8 @@ define i1 @PR6486() nounwind {
 ; CHECK: ret i1 true
 }
 
- at d = common global i32 0, align 4
- at a = common global [1 x i32] zeroinitializer, align 4
+ at d = global i32 0, align 4
+ at a = global [1 x i32] zeroinitializer, align 4
 
 define i1 @PR16462_1() nounwind {
 ; CHECK-LABEL: @PR16462_1(