mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-31 09:32:11 +00:00
a09e18fcfa
This change attempts to simplify (X^Y) -> X or Y in the user's context if we know that
only bits from X or Y are demanded.
A minimized case is provided bellow. This change will simplify "t>>16" into "var1 >>16".
=============================================================
unsigned foo (unsigned val1, unsigned val2) {
unsigned t = val1 ^ 1234;
return (t >> 16) | t; // NOTE: t is used more than once.
}
=============================================================
Note that if the "t" were used only once, the expression would be finally optimized as well.
However, with with this change, the optimization will take place earlier.
Reviewed by Nadav, Thanks a lot!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169317 91177308-0d34-0410-b5e6-96231b3b80d8
85 lines
1.9 KiB
LLVM
85 lines
1.9 KiB
LLVM
; This test makes sure that these instructions are properly eliminated.
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;
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; RUN: opt < %s -instcombine -S | FileCheck %s
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; PR1253
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define i1 @test0(i32 %A) {
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; CHECK: @test0
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; CHECK: %C = icmp slt i32 %A, 0
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%B = xor i32 %A, -2147483648
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%C = icmp sgt i32 %B, -1
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ret i1 %C
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}
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define i1 @test1(i32 %A) {
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; CHECK: @test1
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; CHECK: %C = icmp slt i32 %A, 0
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%B = xor i32 %A, 12345
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%C = icmp slt i32 %B, 0
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ret i1 %C
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}
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; PR1014
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define i32 @test2(i32 %tmp1) {
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; CHECK: @test2
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; CHECK-NEXT: and i32 %tmp1, 32
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; CHECK-NEXT: or i32 %ovm, 8
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; CHECK-NEXT: ret i32
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%ovm = and i32 %tmp1, 32
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%ov3 = add i32 %ovm, 145
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%ov110 = xor i32 %ov3, 153
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ret i32 %ov110
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}
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define i32 @test3(i32 %tmp1) {
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; CHECK: @test3
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; CHECK-NEXT: and i32 %tmp1, 32
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; CHECK-NEXT: or i32 %ovm, 8
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; CHECK-NEXT: ret i32
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%ovm = or i32 %tmp1, 145
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%ov31 = and i32 %ovm, 177
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%ov110 = xor i32 %ov31, 153
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ret i32 %ov110
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}
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define i32 @test4(i32 %A, i32 %B) {
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%1 = xor i32 %A, -1
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%2 = ashr i32 %1, %B
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%3 = xor i32 %2, -1
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ret i32 %3
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; CHECK: @test4
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; CHECK: %1 = ashr i32 %A, %B
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; CHECK: ret i32 %1
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}
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; defect-2 in rdar://12329730
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; (X^C1) >> C2) ^ C3 -> (X>>C2) ^ ((C1>>C2)^C3)
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; where the "X" has more than one use
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define i32 @test5(i32 %val1) {
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test5:
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%xor = xor i32 %val1, 1234
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%shr = lshr i32 %xor, 8
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%xor1 = xor i32 %shr, 1
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%add = add i32 %xor1, %xor
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ret i32 %add
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; CHECK: @test5
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; CHECK: lshr i32 %val1, 8
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; CHECK: ret
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}
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; defect-1 in rdar://12329730
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; Simplify (X^Y) -> X or Y in the user's context if we know that
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; only bits from X or Y are demanded.
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; e.g. the "x ^ 1234" can be optimized into x in the context of "t >> 16".
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; Put in other word, t >> 16 -> x >> 16.
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; unsigned foo(unsigned x) { nsigned t = x ^ 1234; ; return (t >> 16) + t;}
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define i32 @test6(i32 %x) {
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%xor = xor i32 %x, 1234
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%shr = lshr i32 %xor, 16
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%add = add i32 %shr, %xor
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ret i32 %add
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; CHECK: @test6
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; CHECK: lshr i32 %x, 16
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; CHECK: ret
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}
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