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| -rw-r--r-- | lib/Target/PowerPC/README.txt | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt index 70e97f74cd..8834699f63 100644 --- a/lib/Target/PowerPC/README.txt +++ b/lib/Target/PowerPC/README.txt @@ -11,6 +11,35 @@ still a codesize win. ===-------------------------------------------------------------------------=== +We compile the hottest inner loop of viterbi to: + + li r6, 0 + b LBB1_84 ;bb432.i +LBB1_83: ;bb420.i + lbzx r8, r5, r7 + addi r6, r7, 1 + stbx r8, r4, r7 +LBB1_84: ;bb432.i + mr r7, r6 + cmplwi cr0, r7, 143 + bne cr0, LBB1_83 ;bb420.i + +The CBE manages to produce: + + li r0, 143 + mtctr r0 +loop: + lbzx r2, r2, r11 + stbx r0, r2, r9 + addi r2, r2, 1 + bdz later + b loop + +This could be much better (bdnz instead of bdz) but it still beats us. If we +produced this with bdnz, the loop would be a single dispatch group. + +===-------------------------------------------------------------------------=== + Compile: void foo(int *P) { |