David Majnemer 5cbd5a13a4 InstCombine: Properly optimize or'ing bittests together ... CFE, with -03, would turn: bool f(unsigned x) { bool a = x & 1; bool b = x & 2; return a | b; } into: %1 = lshr i32 %x, 1 %2 = or i32 %1, %x %3 = and i32 %2, 1 %4 = icmp ne i32 %3, 0 This sort of thing exposes a nasty pathology in GCC, ICC and LLVM. Instead, we would rather want: %1 = and i32 %x, 3 %2 = icmp ne i32 %1, 0 Things get a bit more interesting in the following case: %1 = lshr i32 %x, %y %2 = or i32 %1, %x %3 = and i32 %2, 1 %4 = icmp ne i32 %3, 0 Replacing it with the following sequence is better: %1 = shl nuw i32 1, %y %2 = or i32 %1, 1 %3 = and i32 %2, %x %4 = icmp ne i32 %3, 0 This sequence is preferable because %1 doesn't involve %x and could potentially be hoisted out of loops if it is invariant; only perform this transform in the non-constant case if we know we won't increase register pressure. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216343 91177308-0d34-0410-b5e6-96231b3b80d8		2014-08-24 09:10:57 +00:00
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CodeGen	[PowerPC] Add support for dcbtst and icbt (prefetch)	2014-08-23 23:21:04 +00:00
DebugInfo	Use DILexicalBlockFile, rather than DILexicalBlock, to track discriminator changes to ensure discriminator changes don't introduce new DWARF DW_TAG_lexical_blocks.	2014-08-21 22:45:21 +00:00
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Instrumentation	[dfsan] Fix non-determinism bug in non-zero label check annotator.	2014-08-22 01:18:18 +00:00
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MC	[PowerPC] Add support for dcbtst and icbt (prefetch)	2014-08-23 23:21:04 +00:00
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tools	llvm-cov: test: add xfail for the big-endian buildbots	2014-08-23 00:47:24 +00:00
Transforms	InstCombine: Properly optimize or'ing bittests together	2014-08-24 09:10:57 +00:00
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