[LSR] Combine unfolded offset into invariant register
LSR reassociates constants as unfolded offsets when the constants fit as
immediate add operands, which currently prevents such constants from being
combined later with loop invariant registers.
This patch modifies GenerateCombinations() to generate a second formula which
includes the unfolded offset in the combined loop-invariant register.
This commit fixes a bug in the original patch (committed at r345114, reverted
at r345123).
Differential Revision: https://reviews.llvm.org/D51861
llvm-svn: 346390
diff --git a/llvm/test/Transforms/LoopStrengthReduce/two-combinations-bug.ll b/llvm/test/Transforms/LoopStrengthReduce/two-combinations-bug.ll
new file mode 100644
index 0000000..21917f5
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/two-combinations-bug.ll
@@ -0,0 +1,55 @@
+; RUN: opt < %s -loop-reduce -S | FileCheck %s
+
+; This test is adapted from the n-body test of the LLVM test-suite: A bug in
+; r345114 caused LSR to generate incorrect code. The test verifies that the
+; induction variable generated for the inner loop depends on the induction
+; variable of the outer loop.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44 = type { double, double, double, double, double, double, double }
+
+; Function Attrs: nounwind uwtable
+define dso_local void @advance(i32 %nbodies, %struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44* nocapture %bodies) local_unnamed_addr #0 {
+; CHECK-LABEL: @advance(
+; CHECK: for.cond.loopexit:
+; CHECK: [[LSR_IV_NEXT:%.*]] = add i64 [[LSR_IV:%.*]], -1
+; CHECK: br label %for.body
+; CHECK: for.body:
+; CHECK: [[LSR_IV]] = phi i64 [ [[LSR_IV_NEXT]]
+; CHECK: br label %for.body3
+; CHECK: for.body3:
+; CHECK: [[LSR_IV1:%.*]] = phi i64 [ [[LSR_IV_NEXT2:%.*]], %for.body3 ], [ [[LSR_IV]], %for.body ]
+; CHECK: [[LSR_IV_NEXT2]] = add i64 [[LSR_IV1]], -1
+; CHECK: [[EXITCOND:%.*]] = icmp eq i64 [[LSR_IV_NEXT2]], 0
+; CHECK: br i1 [[EXITCOND]], label %for.cond.loopexit, label %for.body3
+;
+entry:
+ %wide.trip.count = zext i32 %nbodies to i64
+ br label %for.body
+
+for.cond.loopexit: ; preds = %for.body3
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ br label %for.body
+
+for.body: ; preds = %for.cond.loopexit, %entry
+ %indvars.iv = phi i64 [ 1, %entry ], [ %indvars.iv.next, %for.cond.loopexit ]
+ br label %for.body3
+
+for.body3: ; preds = %for.body3, %for.body
+ %indvars.iv98 = phi i64 [ %indvars.iv, %for.body ], [ %indvars.iv.next99, %for.body3 ]
+ %z9 = getelementptr inbounds %struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44, %struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44* %bodies, i64 %indvars.iv98, i32 2
+ %tmp = load double, double* %z9, align 8, !tbaa !0
+ %indvars.iv.next99 = add nuw nsw i64 %indvars.iv98, 1
+ %exitcond = icmp eq i64 %indvars.iv.next99, %wide.trip.count
+ br i1 %exitcond, label %for.cond.loopexit, label %for.body3
+}
+
+attributes #0 = { nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!0 = !{!1, !2, i64 16}
+!1 = !{!"planet", !2, i64 0, !2, i64 8, !2, i64 16, !2, i64 24, !2, i64 32, !2, i64 40, !2, i64 48}
+!2 = !{!"double", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C/C++ TBAA"}