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Fix regression from my recent GlobalsAA fix.

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There are two fixes here: one, AnalyzeUsesOfPointer can't return
false until it has checked all the uses of the pointer. Two, if a
global uses another global, we have to assume the address of the
first global escapes.

Fixes https://llvm.org/bugs/show_bug.cgi?id=30707 .

Differential Revision: https://reviews.llvm.org/D25798



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285034 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2016-10-24 21:47:44 +00:00
parent 8d980444a4
commit 10310d2d11
2 changed files with 57 additions and 1 deletions
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4
lib/Analysis/GlobalsModRef.cpp
View File

@ -367,7 +367,9 @@ bool GlobalsAAResult::AnalyzeUsesOfPointer(Value *V,
if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
return true; // Allow comparison against null.
} else if (Constant *C = dyn_cast<Constant>(I)) {
return C->isConstantUsed();
// Ignore constants which don't have any live uses.
if (isa<GlobalValue>(C) || C->isConstantUsed())
return true;
} else {
return true;
}

54
test/Analysis/GlobalsModRef/global-used-by-global.ll Normal file
View File

@ -0,0 +1,54 @@
; RUN: opt < %s -globals-aa -gvn -S | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
@a = internal global i32* null, align 8
@b = global i32** @a, align 8
@c = global i32** @a, align 8
@d = common global i32 0, align 4
; Make sure we globals-aa doesn't get confused and allow hoisting
; the load from @a out of the loop.
; CHECK-LABEL: define i32 @main()
; CHECK: for.body:
; CHECK-NEXT: %2 = load i32**, i32*** @b, align 8
; CHECK-NEXT: store i32* @d, i32** %2, align 8
; CHECK-NEXT: %3 = load i32*, i32** @a, align 8
; CHECK-NEXT: %cmp1 = icmp ne i32* %3, @d
; CHECK-NEXT: br i1 %cmp1, label %if.then, label %if.end
define i32 @main() {
entry:
%0 = load i32, i32* @d, align 4
br label %for.cond
for.cond: ; preds = %if.end, %entry
%1 = phi i32 [ %inc, %if.end ], [ %0, %entry ]
%cmp = icmp slt i32 %1, 1
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%2 = load i32**, i32*** @b, align 8
store i32* @d, i32** %2, align 8
%3 = load i32*, i32** @a, align 8
%cmp1 = icmp ne i32* %3, @d
br i1 %cmp1, label %if.then, label %if.end
if.then: ; preds = %for.body
br label %return
if.end: ; preds = %for.body
%4 = load i32, i32* @d, align 4
%inc = add nsw i32 %4, 1
store i32 %inc, i32* @d, align 4
br label %for.cond
for.end: ; preds = %for.cond
br label %return
return: ; preds = %for.end, %if.then
%retval.0 = phi i32 [ 1, %if.then ], [ 0, %for.end ]
ret i32 %retval.0
}