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| -rw-r--r-- | lib/Target/README.txt | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 6c8187cdbf..67aec852fa 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -2295,3 +2295,23 @@ avoids partial register stalls in some important cases. //===---------------------------------------------------------------------===// +We miss an optzn when lowering divide by some constants. For example: + int test(int x) { return x/10; } + +We produce: + +_test: ## @test +## BB#0: ## %entry + movslq %edi, %rax + imulq $1717986919, %rax, %rax ## imm = 0x66666667 + movq %rax, %rcx + shrq $63, %rcx +** shrq $32, %rax +** sarl $2, %eax + addl %ecx, %eax + ret + +The two starred instructions could be replaced with a "sarl $34, %rax". This +occurs in 186.crafty very frequently. + +//===---------------------------------------------------------------------===// |