RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-23 03:02:36 +01:00
Code Issues Projects Releases Wiki Activity

Make GlobalsAA ignore dead constant expressions.

Browse Source 
Slightly improves the precision of GlobalsAA in certain situations, and
makes the behavior of optimization passes more predictable.

Differential Revision: https://reviews.llvm.org/D24104

llvm-svn: 283165
This commit is contained in:
Eli Friedman 2016-10-04 00:03:55 +00:00
parent 632cfe0b14
commit 6579a1a109
2 changed files with 56 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
lib/Analysis/GlobalsModRef.cpp
View File

@ -366,6 +366,8 @@ bool GlobalsAAResult::AnalyzeUsesOfPointer(Value *V,
} else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
return true; // Allow comparison against null.
} else if (Constant *C = dyn_cast<Constant>(I)) {
return C->isConstantUsed();
} else {
return true;
}

54
test/Analysis/GlobalsModRef/dead-uses.ll Normal file
View File

@ -0,0 +1,54 @@
; RUN: opt < %s -instcombine -globals-aa -licm -S | FileCheck %s
; Make sure -globals-aa ignores dead uses of globals.
@a = internal global i32 0, align 4
@c = common global i32 0, align 4
; Function Attrs: nounwind
define i32 @g() {
; Make sure the load of @a is hoisted.
; CHECK-LABEL: define i32 @g()
; CHECK: entry:
; CHECK-NEXT: load i32, i32* @a, align 4
; CHECK-NEXT: br label %for.cond
entry:
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%sum.0 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
%cmp = icmp slt i32 %i.0, 1000
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%0 = load i32, i32* @a, align 4
%add = add nsw i32 %sum.0, %0
call void @f()
br label %for.inc
for.inc: ; preds = %for.body
%inc = add nsw i32 %i.0, 1
br label %for.cond
for.end: ; preds = %for.cond
ret i32 %sum.0
}
; Function Attrs: nounwind
define internal void @f() {
entry:
%tobool = icmp ne i32 0, 0
br i1 %tobool, label %if.then, label %if.end
if.then: ; preds = %entry
store i32 ptrtoint (i32* @a to i32), i32* @c, align 4
br label %if.end
if.end: ; preds = %if.then, %entry
%0 = load i32, i32* @c, align 4
%inc = add nsw i32 %0, 1
store i32 %inc, i32* @c, align 4
ret void
}