Changes in directory llvm/lib/Target/PowerPC:
README.txt updated: 1.49 -> 1.50 --- Log message: example nate pointed out --- Diffs of the changes: (+33 -0) README.txt | 33 +++++++++++++++++++++++++++++++++ 1 files changed, 33 insertions(+) Index: llvm/lib/Target/PowerPC/README.txt diff -u llvm/lib/Target/PowerPC/README.txt:1.49 llvm/lib/Target/PowerPC/README.txt:1.50 --- llvm/lib/Target/PowerPC/README.txt:1.49 Mon Jan 30 20:55:28 2006 +++ llvm/lib/Target/PowerPC/README.txt Tue Jan 31 01:16:34 2006 @@ -427,3 +427,36 @@ without the lwz/stw's. +===-------------------------------------------------------------------------=== + +Compile this: + +int foo(int a) { + int b = (a < 8); + if (b) { + return b * 3; // ignore the fact that this is always 3. + } else { + return 2; + } +} + +into something not this: + +_foo: +1) cmpwi cr7, r3, 8 + mfcr r2, 1 + rlwinm r2, r2, 29, 31, 31 +1) cmpwi cr0, r3, 7 + bgt cr0, LBB1_2 ; UnifiedReturnBlock +LBB1_1: ; then + rlwinm r2, r2, 0, 31, 31 + mulli r3, r2, 3 + blr +LBB1_2: ; UnifiedReturnBlock + li r3, 2 + blr + +In particular, the two compares (marked 1) could be shared by reversing one. +This could be done in the dag combiner, by swapping a BR_CC when a SETCC of the +same operands (but backwards) exists. In this case, this wouldn't save us +anything though, because the compares still wouldn't be shared. _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits