[PATCH] D42263: [ARM] Fix perf regression in compare optimization.
Joel Galenson via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 18 13:11:15 PST 2018
jgalenson created this revision.
jgalenson added reviewers: efriedma, rogfer01, eastig.
Herald added subscribers: kristof.beyls, javed.absar, aemerson.
Fix a performance regression caused by r322737.
While trying to make it easier to replace compares with existing adds and subtracts, I accidentally stopped it from doing so in some cases. This should fix that.
https://reviews.llvm.org/D42263
Files:
lib/Target/ARM/ARMBaseInstrInfo.cpp
test/CodeGen/ARM/overflow-intrinsic-optimizations.ll
Index: test/CodeGen/ARM/overflow-intrinsic-optimizations.ll
===================================================================
--- test/CodeGen/ARM/overflow-intrinsic-optimizations.ll
+++ test/CodeGen/ARM/overflow-intrinsic-optimizations.ll
@@ -197,6 +197,38 @@
declare void @external_fn(...) local_unnamed_addr #0
+define i32 @are_equal(i32* nocapture readonly %a1, i32* nocapture readonly %a2, i32 %n) local_unnamed_addr #0 {
+; CHECK-LABEL: are_equal
+; CHECK: subs r{{[0-9]+}}, r{{[0-9]+}}, #1
+; CHECK-NEXT: bne
+entry:
+ %tobool7 = icmp eq i32 %n, 0
+ br i1 %tobool7, label %while.end, label %land.rhs.preheader
+
+land.rhs.preheader:
+ br label %land.rhs
+
+while.cond:
+ %tobool = icmp eq i32 %dec9, 0
+ br i1 %tobool, label %while.end, label %land.rhs
+
+land.rhs:
+ %dec9.in = phi i32 [ %dec9, %while.cond ], [ %n, %land.rhs.preheader ]
+ %dec9 = add nsw i32 %dec9.in, -1
+ %arrayidx = getelementptr inbounds i32, i32* %a1, i32 %dec9
+ %0 = load i32, i32* %arrayidx, align 4
+ %arrayidx1 = getelementptr inbounds i32, i32* %a2, i32 %dec9
+ %1 = load i32, i32* %arrayidx1, align 4
+ %cmp = icmp eq i32 %0, %1
+ br i1 %cmp, label %while.cond, label %while.end
+
+while.end:
+ %n.addr.0.lcssa = phi i32 [ 0, %entry ], [ 0, %while.cond ], [ %dec9.in, %land.rhs ]
+ %cmp2 = icmp slt i32 %n.addr.0.lcssa, 1
+ %conv = zext i1 %cmp2 to i32
+ ret i32 %conv
+}
+
declare void @llvm.trap() #2
declare { i32, i1 } @llvm.sadd.with.overflow.i32(i32, i32) #1
declare { i32, i1 } @llvm.uadd.with.overflow.i32(i32, i32) #1
Index: lib/Target/ARM/ARMBaseInstrInfo.cpp
===================================================================
--- lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -2764,7 +2764,7 @@
if (I == B)
// The 'and' is below the comparison instruction.
- return false;
+ break;
}
// Return false if no candidates exist.
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