diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 3ee32cce05..84e1532284 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -734,3 +734,30 @@ _foo: ret //===---------------------------------------------------------------------===// + +Consider the expansion of: + +uint %test3(uint %X) { + %tmp1 = rem uint %X, 255 + ret uint %tmp1 +} + +Currently it compiles to: + +... + movl $2155905153, %ecx + movl 8(%esp), %esi + movl %esi, %eax + mull %ecx +... + +This could be "reassociated" into: + + movl $2155905153, %eax + movl 8(%esp), %ecx + mull %ecx + +to avoid the copy. In fact, the existing two-address stuff would do this +except that mul isn't a commutative 2-addr instruction. I guess this has +to be done at isel time based on the #uses to mul? + |