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a037cc62b6
In searching for a fix for the underlying code-quality bug highlighted by r246937 (that SDAG simplification can lead to us generating an ISD::OR node with a constant zero LHS), I ran across this: We generically canonicalize commutative binary-operation nodes in SDAG getNode so that, if only one operand is a constant, it will be on the RHS. However, we were doing this only after a bunch of constant-based simplification checks that all assume this canonical form (that any constant will be on the RHS). Moving the operand-swapping canonicalization prior to these checks seems like the right thing to do (and, as it turns out, causes SDAG to completely fold away the computation in test/CodeGen/ARM/2012-11-14-subs_carry.ll, just like InstCombine would do). llvm-svn: 246938
36 lines
805 B
LLVM
36 lines
805 B
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-ios -arm-atomic-cfg-tidy=0 | FileCheck %s
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;CHECK-LABEL: foo:
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;CHECK: movs r0, #0
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;CHECK-NEXT: bx lr
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; Note: This test case originally checked, per r167963, for:
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; adds
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; adc
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; bx
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; But SDAG now, like InstCombine, can fold everything away.
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;rdar://12028498
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define i32 @foo() nounwind ssp {
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entry:
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%tmp2 = zext i32 3 to i64
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br label %bug_block
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bug_block:
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%tmp410 = and i64 1031, 1647010
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%tmp411 = and i64 %tmp2, -211
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%tmp412 = shl i64 %tmp410, %tmp2
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%tmp413 = shl i64 %tmp411, %tmp2
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%tmp415 = and i64 %tmp413, 1
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%tmp420 = xor i64 0, %tmp415
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%tmp421 = and i64 %tmp412, %tmp415
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%tmp422 = shl i64 %tmp421, 1
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br label %finish
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finish:
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%tmp423 = lshr i64 %tmp422, 32
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%tmp424 = trunc i64 %tmp423 to i32
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ret i32 %tmp424
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}
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