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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DSE,MSSA] Implement eliminating 'noop' stores"
href="https://bugs.llvm.org/show_bug.cgi?id=45795">45795</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[DSE,MSSA] Implement eliminating 'noop' stores
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>florian_hahn@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>The MemorySSA-backed DSE does not yet support eliminating redundant 'noop'
stores, where the store stores a value just loaded from the same address like
in the examples below:
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -basicaa -dse -S | FileCheck %s
; RUN: opt < %s -aa-pipeline=basic-aa -passes=dse -S | FileCheck %s
target datalayout =
"E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
define void @test5(i32* %Q) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: [[A:%.*]] = load volatile i32, i32* [[Q:%.*]]
; CHECK-NEXT: ret void
;
%a = load volatile i32, i32* %Q
store i32 %a, i32* %Q
ret void
}
; PR2599 - load -> store to same address.
define void @test12({ i32, i32 }* %x) nounwind {
; CHECK-LABEL: @test12(
; CHECK-NEXT: [[TMP7:%.*]] = getelementptr { i32, i32 }, { i32, i32 }*
[[X:%.*]], i32 0, i32 1
; CHECK-NEXT: [[TMP8:%.*]] = load i32, i32* [[TMP7]], align 4
; CHECK-NEXT: [[TMP17:%.*]] = sub i32 0, [[TMP8]]
; CHECK-NEXT: store i32 [[TMP17]], i32* [[TMP7]], align 4
; CHECK-NEXT: ret void
;
%tmp4 = getelementptr { i32, i32 }, { i32, i32 }* %x, i32 0, i32 0
%tmp5 = load i32, i32* %tmp4, align 4
%tmp7 = getelementptr { i32, i32 }, { i32, i32 }* %x, i32 0, i32 1
%tmp8 = load i32, i32* %tmp7, align 4
%tmp17 = sub i32 0, %tmp8
store i32 %tmp5, i32* %tmp4, align 4
store i32 %tmp17, i32* %tmp7, align 4
ret void
}
; Remove redundant store if loaded value is in another block.
define i32 @test26(i1 %c, i32* %p) {
; CHECK-LABEL: @test26(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[C:%.*]], label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: ret i32 0
;
entry:
%v = load i32, i32* %p, align 4
br i1 %c, label %bb1, label %bb2
bb1:
br label %bb3
bb2:
store i32 %v, i32* %p, align 4
br label %bb3
bb3:
ret i32 0
}
; Remove redundant store if loaded value is in another block.
define i32 @test27(i1 %c, i32* %p) {
; CHECK-LABEL: @test27(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[C:%.*]], label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: ret i32 0
;
entry:
%v = load i32, i32* %p, align 4
br i1 %c, label %bb1, label %bb2
bb1:
br label %bb3
bb2:
br label %bb3
bb3:
store i32 %v, i32* %p, align 4
ret i32 0
}
; Remove redundant store if loaded value is in another block inside a loop.
define i32 @test31(i1 %c, i32* %p, i32 %i) {
; CHECK-LABEL: @test31(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br i1 undef, label [[BB1]], label [[BB2:%.*]]
; CHECK: bb2:
; CHECK-NEXT: ret i32 0
;
entry:
%v = load i32, i32* %p, align 4
br label %bb1
bb1:
store i32 %v, i32* %p, align 4
br i1 undef, label %bb1, label %bb2
bb2:
ret i32 0
}
; Remove redundant store, which is in the lame loop as the load.
define i32 @test33(i1 %c, i32* %p, i32 %i) {
; CHECK-LABEL: @test33(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB2:%.*]]
; CHECK: bb2:
; CHECK-NEXT: call void @unknown_func()
; CHECK-NEXT: br i1 undef, label [[BB1]], label [[BB3:%.*]]
; CHECK: bb3:
; CHECK-NEXT: ret i32 0
;
entry:
br label %bb1
bb1:
%v = load i32, i32* %p, align 4
br label %bb2
bb2:
store i32 %v, i32* %p, align 4
; Might read and overwrite value at %p, but doesn't matter.
call void @unknown_func()
br i1 undef, label %bb1, label %bb3
bb3:
ret i32 0
}
declare void @unknown_func()</pre>
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