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A couple minor README updates.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91823 91177308-0d34-0410-b5e6-96231b3b80d8
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Eli Friedman 2009-12-21 08:03:16 +00:00
parent b6219ba3d6
commit 1f1b0f748d
1 changed files with 5 additions and 14 deletions
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19
lib/Target/X86/README.txt
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@ -123,20 +123,6 @@ when it can invert the result of the compare for free.
//===---------------------------------------------------------------------===//
How about intrinsics? An example is:
*res = _mm_mulhi_epu16(*A, _mm_mul_epu32(*B, *C));
compiles to
pmuludq (%eax), %xmm0
movl 8(%esp), %eax
movdqa (%eax), %xmm1
pmulhuw %xmm0, %xmm1
The transformation probably requires a X86 specific pass or a DAG combiner
target specific hook.
//===---------------------------------------------------------------------===//
In many cases, LLVM generates code like this:
_test:
@ -1762,6 +1748,11 @@ LBB1_1: ## bb1
cmpl $150, %edi
jne LBB1_1 ## bb1
The issue is that we hoist the cast of "scaler" to long long outside of the
loop, the value comes into the loop as two values, and
RegsForValue::getCopyFromRegs doesn't know how to put an AssertSext on the
constructed BUILD_PAIR which represents the cast value.
//===---------------------------------------------------------------------===//
Test instructions can be eliminated by using EFLAGS values from arithmetic