llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-15 07:34:33 +00:00

History

Chris Lattner c739cd6d07 my recent change caused a failure in a bswap testcase, because it changed

the order that instcombine processed instructions in the testcase.  The end
result is that instcombine finished with:

define i16 @test1(i16 %a) {
        %tmp = zext i16 %a to i32               ; <i32> [#uses=2]
        %tmp21 = lshr i32 %tmp, 8               ; <i32> [#uses=1]
        %tmp5 = shl i32 %tmp, 8         ; <i32> [#uses=1]
        %tmp.upgrd.32 = or i32 %tmp21, %tmp5            ; <i32> [#uses=1]
        %tmp.upgrd.3 = trunc i32 %tmp.upgrd.32 to i16           ; <i16> [#uses=1]
        ret i16 %tmp.upgrd.3
}

which can't get matched as a bswap.

This patch makes instcombine more sophisticated about removing truncating
casts, allowing it to turn this into:

define i16 @test2(i16 %a) {
        %tmp211 = lshr i16 %a, 8
        %tmp52 = shl i16 %a, 8
        %tmp.upgrd.323 = or i16 %tmp211, %tmp52
        ret i16 %tmp.upgrd.323
}

which then matches as bswap.  This fixes bswap.ll and implements
InstCombine/cast2.ll:test[12].  This also implements cast elimination of
add/sub.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34870 91177308-0d34-0410-b5e6-96231b3b80d8

2007-03-03 05:27:34 +00:00

Analysis

Fix an unequal bitwidth issue.

2007-03-02 02:59:25 +00:00