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Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 1f67bee..4d2d4b6 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -319,3 +319,16 @@ entry: } //===---------------------------------------------------------------------===// + +-instcombine should handle this transform: + setcc (sdiv X / C1 ), C2 +when X, C1, and C2 are unsigned. Similarly for udiv and signed operands. + +Currently InstCombine avoids this transform but will do it when the signs of +the operands and the sign of the divide match. See the FIXME in +InstructionCombining.cpp in the visitSetCondInst method after the switch case +for Instruction::UDiv (around line 4447) for more details. + +The SingleSource/Benchmarks/Shootout-C++/hash and hash2 tests have examples of +this construct. +//===---------------------------------------------------------------------===// |