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| author | Chris Lattner <sabre@nondot.org> | 2011-01-18 07:47:48 +0000 |
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| committer | Chris Lattner <sabre@nondot.org> | 2011-01-18 07:47:48 +0000 |
| commit | 908d8e82b5cc19d1a0a55a5fbc9dfd87359d726e (patch) | |
| tree | 597a69542e25926f1dbeed4fb0ca87697a2c51e7 /lib/Target/README.txt | |
| parent | 899407533ac26ff0ff827631bd5164b67548272f (diff) | |
| download | llvm-908d8e82b5cc19d1a0a55a5fbc9dfd87359d726e.tar.gz llvm-908d8e82b5cc19d1a0a55a5fbc9dfd87359d726e.tar.bz2 llvm-908d8e82b5cc19d1a0a55a5fbc9dfd87359d726e.tar.xz | |
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123752 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/README.txt')
| -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. + +//===---------------------------------------------------------------------===// |