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6a7770b7ae
This changes the SelectionDAG scheduling preference to source order. Soon, the SelectionDAG scheduler can be bypassed saving a nice chunk of compile time. Performance differences that result from this change are often a consequence of register coalescing. The register coalescer is far from perfect. Bugs can be filed for deficiencies. On x86 SandyBridge/Haswell, the source order schedule is often preserved, particularly for small blocks. Register pressure is generally improved over the SD scheduler's ILP mode. However, we are still able to handle large blocks that require latency hiding, unlike the SD scheduler's BURR mode. MI scheduler also attempts to discover the critical path in single-block loops and adjust heuristics accordingly. The MI scheduler relies on the new machine model. This is currently unimplemented for AVX, so we may not be generating the best code yet. Unit tests are updated so they don't depend on SD scheduling heuristics. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192750 91177308-0d34-0410-b5e6-96231b3b80d8
27 lines
1.1 KiB
LLVM
27 lines
1.1 KiB
LLVM
; REQUIRES: asserts
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; RUN: llc < %s -march=x86 -relocation-model=static -stats 2>&1 | \
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; RUN: grep asm-printer | grep 16
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;
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; It's possible to schedule this in 14 instructions by avoiding
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; callee-save registers, but the scheduler isn't currently that
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; conervative with registers.
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@size20 = external global i32 ; <i32*> [#uses=1]
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@in5 = external global i8* ; <i8**> [#uses=1]
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define i32 @compare(i8* %a, i8* %b) nounwind {
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%tmp = bitcast i8* %a to i32* ; <i32*> [#uses=1]
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%tmp1 = bitcast i8* %b to i32* ; <i32*> [#uses=1]
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%tmp.upgrd.1 = load i32* @size20 ; <i32> [#uses=1]
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%tmp.upgrd.2 = load i8** @in5 ; <i8*> [#uses=2]
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%tmp3 = load i32* %tmp1 ; <i32> [#uses=1]
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%gep.upgrd.3 = zext i32 %tmp3 to i64 ; <i64> [#uses=1]
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%tmp4 = getelementptr i8* %tmp.upgrd.2, i64 %gep.upgrd.3 ; <i8*> [#uses=2]
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%tmp7 = load i32* %tmp ; <i32> [#uses=1]
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%gep.upgrd.4 = zext i32 %tmp7 to i64 ; <i64> [#uses=1]
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%tmp8 = getelementptr i8* %tmp.upgrd.2, i64 %gep.upgrd.4 ; <i8*> [#uses=2]
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%tmp.upgrd.5 = tail call i32 @memcmp( i8* %tmp8, i8* %tmp4, i32 %tmp.upgrd.1 ) ; <i32> [#uses=1]
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ret i32 %tmp.upgrd.5
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}
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declare i32 @memcmp(i8*, i8*, i32)
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