llvm-6502/test/Transforms/InstCombine/2010-11-01-lshr-mask.ll
Shuxin Yang a09e18fcfa For rdar://12329730, last piece.
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
2012-12-04 22:15:32 +00:00

47 lines
1.1 KiB
LLVM

; RUN: opt -instcombine -S < %s | FileCheck %s
; <rdar://problem/8606771>
; CHECK: @main
define i32 @main(i32 %argc) nounwind ssp {
entry:
%tmp3151 = trunc i32 %argc to i8
; CHECK: %0 = shl i8 %tmp3151, 5
; CHECK: and i8 %0, 64
; CHECK-NOT: shl
; CHECK-NOT: shr
%tmp3161 = or i8 %tmp3151, -17
%tmp3162 = and i8 %tmp3151, 122
%tmp3163 = xor i8 %tmp3162, -17
%tmp4114 = shl i8 %tmp3163, 6
%tmp4115 = xor i8 %tmp4114, %tmp3163
%tmp4120 = xor i8 %tmp3161, %tmp4115
%tmp4126 = lshr i8 %tmp4120, 7
%tmp4127 = mul i8 %tmp4126, 64
%tmp4086 = zext i8 %tmp4127 to i32
; CHECK: ret i32
ret i32 %tmp4086
}
; rdar://8739316
; CHECK: @foo
define i8 @foo(i8 %arg, i8 %arg1) nounwind {
bb:
%tmp = shl i8 %arg, 7
%tmp2 = and i8 %arg1, 84
%tmp3 = and i8 %arg1, -118
%tmp4 = and i8 %arg1, 33
%tmp5 = sub i8 -88, %tmp2
%tmp6 = and i8 %tmp5, 84
%tmp7 = or i8 %tmp4, %tmp6
%tmp8 = xor i8 %tmp, %tmp3
%tmp9 = or i8 %tmp7, %tmp8
%tmp10 = lshr i8 %tmp8, 7
%tmp11 = shl i8 %tmp10, 5
; CHECK: %tmp10 = lshr i8 %tmp8, 7
; CHECK: %tmp11 = shl nuw nsw i8 %tmp10, 5
%tmp12 = xor i8 %tmp11, %tmp9
ret i8 %tmp12
}