ff36411b23
This PR fixes https://github.com/llvm/llvm-project/issues/55013 : the max intrinsics is not generated for this simple loop case : https://godbolt.org/z/hxz1xhMPh. This is caused by a ICMP not being folded into a select, thus not generating the max intrinsics. For the story : Since LLVM 14, SCCP pass got smarter by folding sext into zext for positive ranges : https://reviews.llvm.org/D81756. After this change, InstCombine was sometimes unable to fold ICMP correctly as both of the arguments pointed to mismatched zext/sext. To fix this, @rotateright implemented this fix : https://reviews.llvm.org/D124419 that tries to resolve the mismatch by knowing if the argument of a zext is positive (in which case, it is like a sext) by using ValueTracking, however ValueTracking is not smart enough to infer that the value is positive in some cases. Recently, @nikic implemented #67982 which keeps the information that a zext is non-negative. This PR simply uses this information to do the folding accordingly. TLDR : This PR uses the recent nneg tag on zext to fold the icmp accordingly in instcombine. This PR also contains test cases for sext/zext folding with InstCombine as well as a x86 regression tests for the max/min case.
112 lines
3.5 KiB
LLVM
112 lines
3.5 KiB
LLVM
; RUN: opt < %s -O3 -S | FileCheck %s
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; See issue #55013 and PR #70845 for more details.
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; This test comes from the following C program, compiled with clang
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;
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;; short vecreduce_smin_v2i16(int n, short* v)
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;; {
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;; short p = 0;
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;; for (int i = 0; i < n; ++i)
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;; p = p > v[i] ? v[i] : p;
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;; return p;
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;; }
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;
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;; short vecreduce_smax_v2i16(int n, short* v)
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;; {
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;; short p = 0;
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;; for (int i = 0; i < n; ++i)
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;; p = p < v[i] ? v[i] : p;
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;; return p;
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;; }
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define i16 @vecreduce_smin_v2i16(i32 %n, ptr %v) {
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; CHECK-LABEL: define i16 @vecreduce_smin_v2i16(
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; CHECK: @llvm.smin.v2i16
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entry:
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%p.0 = phi i16 [ 0, %entry ], [ %conv8, %for.inc ]
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
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%cmp = icmp slt i32 %i.0, %n
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br i1 %cmp, label %for.body, label %for.end
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for.body: ; preds = %for.cond
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%conv = sext i16 %p.0 to i32
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%idxprom = sext i32 %i.0 to i64
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%arrayidx = getelementptr inbounds i16, ptr %v, i64 %idxprom
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%0 = load i16, ptr %arrayidx, align 2
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%conv1 = sext i16 %0 to i32
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%cmp2 = icmp sgt i32 %conv, %conv1
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br i1 %cmp2, label %cond.true, label %cond.false
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cond.true: ; preds = %for.body
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%idxprom4 = sext i32 %i.0 to i64
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%arrayidx5 = getelementptr inbounds i16, ptr %v, i64 %idxprom4
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%1 = load i16, ptr %arrayidx5, align 2
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%conv6 = sext i16 %1 to i32
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br label %cond.end
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cond.false: ; preds = %for.body
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%conv7 = sext i16 %p.0 to i32
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br label %cond.end
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cond.end: ; preds = %cond.false, %cond.true
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%cond = phi i32 [ %conv6, %cond.true ], [ %conv7, %cond.false ]
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%conv8 = trunc i32 %cond to i16
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br label %for.inc
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for.inc: ; preds = %cond.end
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%inc = add nsw i32 %i.0, 1
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br label %for.cond
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for.end: ; preds = %for.cond
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ret i16 %p.0
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}
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define i16 @vecreduce_smax_v2i16(i32 %n, ptr %v) {
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; CHECK-LABEL: define i16 @vecreduce_smax_v2i16(
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; CHECK: @llvm.smax.v2i16
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entry:
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%p.0 = phi i16 [ 0, %entry ], [ %conv8, %for.inc ]
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
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%cmp = icmp slt i32 %i.0, %n
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br i1 %cmp, label %for.body, label %for.end
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for.body: ; preds = %for.cond
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%conv = sext i16 %p.0 to i32
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%idxprom = sext i32 %i.0 to i64
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%arrayidx = getelementptr inbounds i16, ptr %v, i64 %idxprom
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%0 = load i16, ptr %arrayidx, align 2
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%conv1 = sext i16 %0 to i32
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%cmp2 = icmp slt i32 %conv, %conv1
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br i1 %cmp2, label %cond.true, label %cond.false
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cond.true: ; preds = %for.body
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%idxprom4 = sext i32 %i.0 to i64
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%arrayidx5 = getelementptr inbounds i16, ptr %v, i64 %idxprom4
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%1 = load i16, ptr %arrayidx5, align 2
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%conv6 = sext i16 %1 to i32
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br label %cond.end
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cond.false: ; preds = %for.body
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%conv7 = sext i16 %p.0 to i32
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br label %cond.end
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cond.end: ; preds = %cond.false, %cond.true
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%cond = phi i32 [ %conv6, %cond.true ], [ %conv7, %cond.false ]
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%conv8 = trunc i32 %cond to i16
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br label %for.inc
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for.inc: ; preds = %cond.end
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%inc = add nsw i32 %i.0, 1
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br label %for.cond
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for.end: ; preds = %for.cond
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ret i16 %p.0
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}
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