diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 3e40027..b8db3ab 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -668,3 +668,37 @@ do not make use of. //===---------------------------------------------------------------------===// We should handle __attribute__ ((__visibility__ ("hidden"))). + +//===---------------------------------------------------------------------===// + +Consider: +int foo(int *a, int t) { +int x; +for (x=0; x<40; ++x) + t = t + a[x] + x; +return t; +} + +We generate: +LBB1_1: #cond_true + movl %ecx, %esi + movl (%edx,%eax,4), %edi + movl %esi, %ecx + addl %edi, %ecx + addl %eax, %ecx + incl %eax + cmpl $40, %eax + jne LBB1_1 #cond_true + +GCC generates: + +L2: + addl (%ecx,%edx,4), %eax + addl %edx, %eax + addl $1, %edx + cmpl $40, %edx + jne L2 + +Smells like a register coallescing/reassociation issue. + +//===---------------------------------------------------------------------===// |