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| author | Torok Edwin <edwintorok@gmail.com> | 2009-05-23 17:29:48 +0000 |
|---|---|---|
| committer | Torok Edwin <edwintorok@gmail.com> | 2009-05-23 17:29:48 +0000 |
| commit | be6a9a151adb3e9b47f45a10d31f451fd461720f (patch) | |
| tree | 82bb0b35d97239e3076ef46056d41889d04b63c4 /llvm/test/CodeGen | |
| parent | ba74e5daa58fd7d65e5ff2929b7712e83299c097 (diff) | |
| download | bcm5719-llvm-be6a9a151adb3e9b47f45a10d31f451fd461720f.tar.gz bcm5719-llvm-be6a9a151adb3e9b47f45a10d31f451fd461720f.zip | |
Fix PR4254.
The DAGCombiner created a negative shiftamount, stored in an
unsigned variable. Later the optimizer eliminated the shift entirely as being
undefined.
Example: (srl (shl X, 56) 48). ShiftAmt is 4294967288.
Fix it by checking that the shiftamount is positive, and storing in a signed
variable.
llvm-svn: 72331
Diffstat (limited to 'llvm/test/CodeGen')
| -rw-r--r-- | llvm/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/llvm/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll b/llvm/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll new file mode 100644 index 00000000000..6f2bef4fca1 --- /dev/null +++ b/llvm/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll @@ -0,0 +1,14 @@ +; RUN: llvm-as < %s | llc | grep -E {sar|shl|mov|or} | count 4 +; Check that the shr(shl X, 56), 48) is not mistakenly turned into +; a shr (X, -8) that gets subsequently "optimized away" as undef +; PR4254 +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128" +target triple = "x86_64-unknown-linux-gnu" + +define i64 @foo(i64 %b) nounwind readnone { +entry: + %shl = shl i64 %b, 56 ; <i64> [#uses=1] + %shr = ashr i64 %shl, 48 ; <i64> [#uses=1] + %add5 = or i64 %shr, 1 ; <i64> [#uses=1] + ret i64 %add5 +} |
