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a3c6b40b1a
The motivation for filling out these select-of-constants cases goes back to D24480, where we discussed removing an IR fold from add(zext) --> select. And that goes back to: https://reviews.llvm.org/rL75531 https://reviews.llvm.org/rL159230 The idea is that we should always canonicalize patterns like this to a select-of-constants in IR because that's the smallest IR and the best for value tracking. Note that we currently do the opposite in some cases (like the cases in *this* patch). Ie, the proposed folds in this patch already exist in InstCombine today: https://github.com/llvm-mirror/llvm/blob/master/lib/Transforms/InstCombine/InstCombineSelect.cpp#L1151 As this patch shows, most targets generate better machine code for simple ext/add/not ops rather than a select of constants. So the follow-up steps to make this less of a patchwork of special-case folds and missing IR canonicalization: 1. Have DAGCombiner convert any select of constants into ext/add/not ops. 2 Have InstCombine canonicalize in the other direction (create more selects). Differential Revision: https://reviews.llvm.org/D30180 llvm-svn: 296137
20 lines
553 B
LLVM
20 lines
553 B
LLVM
; RUN: llc < %s -march=nvptx -mcpu=sm_20 | FileCheck %s
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
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define void @foo(i64 %a, i64 %add, i128* %retptr) {
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; CHECK: add.s64
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; CHECK: setp.lt.u64
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; CHECK: setp.lt.u64
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; CHECK: selp.u64
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; CHECK: selp.b64
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; CHECK: add.s64
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%t1 = sext i64 %a to i128
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%add2 = zext i64 %add to i128
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%val = add i128 %t1, %add2
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store i128 %val, i128* %retptr
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ret void
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}
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