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https://github.com/c64scene-ar/llvm-6502.git
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4d2a706176
up to where it actually works as intended. The problem is that a GlobalAlias isa GlobalValue and so the prior block handled all of the cases. This allows us to constant fold based on the actual constant expression in the global alias. As an example, see the last function in the newly added test case which explicitly aligns an unaligned pointer using constant expression math. Without this change, we fail to see that and fold an alignment test to zero. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220164 91177308-0d34-0410-b5e6-96231b3b80d8
41 lines
1.2 KiB
LLVM
41 lines
1.2 KiB
LLVM
; RUN: opt -S < %s -instcombine | FileCheck %s
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target datalayout = "e-p1:16:16-p2:32:32-p3:64:64"
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@G1 = global i32 42, align 1
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@G2 = global i32 42
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@G3 = global [4 x i8] zeroinitializer, align 1
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@A1 = alias bitcast (i8* getelementptr inbounds ([4 x i8]* @G3, i32 0, i32 2) to i32*)
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@A2 = alias inttoptr (i64 and (i64 ptrtoint (i8* getelementptr inbounds ([4 x i8]* @G3, i32 0, i32 3) to i64), i64 -4) to i32*)
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define i64 @f1() {
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; This cannot be constant folded because G1 is underaligned.
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; CHECK-LABEL: @f1(
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; CHECK: ret i64 and
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ret i64 and (i64 ptrtoint (i32* @G1 to i64), i64 1)
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}
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define i64 @f2() {
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; The preferred alignment for G2 allows this one to foled to zero.
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; CHECK-LABEL: @f2(
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; CHECK: ret i64 0
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ret i64 and (i64 ptrtoint (i32* @G2 to i64), i64 1)
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}
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define i64 @g1() {
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; This cannot be constant folded because A1 aliases G3 which is underalaigned.
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; CHECK-LABEL: @g1(
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; CHECK: ret i64 and
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ret i64 and (i64 ptrtoint (i32* @A1 to i64), i64 1)
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}
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define i64 @g2() {
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; While A2 also aliases G3 which is underaligned, the math of A2 forces a
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; certain alignment allowing this to fold to zero.
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; CHECK-LABEL: @g2(
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; CHECK: ret i64 0
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ret i64 and (i64 ptrtoint (i32* @A2 to i64), i64 1)
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}
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