[PATCH] D156458: GVNSink: add test to show GVN-aware sinking

[Ramkumar Ramachandra via Phabricator via llvm-commits]

artagnon created this revision.
artagnon added reviewers: jmolloy, jeroen.dobbelaere, nikic, lebedev.ri, xbolva00.
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artagnon requested review of this revision.
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As a follow-up to D156451 <https://reviews.llvm.org/D156451>, add a test corresponding to the following
program, after running it through GVN:

  void BeamFormWeights(int a[20000], int beam) {
    for (int i = 0; i < 10000; ++i) {
      if (i == beam)
        a[2 * i] = 0;
      else
        a[2 * i] = 1;
    }
  }

Sinking in this particular case is particularly challenging, and can
only be done by a GVN-aware sinking pass.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156458

Files:
  llvm/test/Transforms/GVNSink/gvn-awareness.ll


Index: llvm/test/Transforms/GVNSink/gvn-awareness.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/GVNSink/gvn-awareness.ll
@@ -0,0 +1,90 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; Test to show a sinking operation that would have been impossible without
+; GVN-awareness.
+; RUN: opt -passes=gvn-sink -S < %s | FileCheck %s
+
+define void @gvn_awareness(ptr %a, i32 %beam) {
+; CHECK-LABEL: define void @gvn_awareness
+; CHECK-SAME: (ptr [[A:%.*]], i32 [[BEAM:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[A_ADDR:%.*]] = alloca ptr, align 8
+; CHECK-NEXT:    [[BEAM_ADDR:%.*]] = alloca i32, align 4
+; CHECK-NEXT:    [[I:%.*]] = alloca i32, align 4
+; CHECK-NEXT:    store ptr [[A]], ptr [[A_ADDR]], align 8
+; CHECK-NEXT:    store i32 [[BEAM]], ptr [[BEAM_ADDR]], align 4
+; CHECK-NEXT:    br label [[FOR_COND:%.*]]
+; CHECK:       for.cond:
+; CHECK-NEXT:    [[DOTSINK:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[INC:%.*]], [[IF_END:%.*]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = phi ptr [ [[TMP3:%.*]], [[IF_END]] ], [ [[A]], [[ENTRY]] ]
+; CHECK-NEXT:    [[TMP1:%.*]] = phi i32 [ [[INC]], [[IF_END]] ], [ 0, [[ENTRY]] ]
+; CHECK-NEXT:    store i32 [[DOTSINK]], ptr [[I]], align 4
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[TMP1]], 10000
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY:%.*]], label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+; CHECK:       for.body:
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i32 [[TMP1]], [[BEAM]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[MUL:%.*]] = mul nsw i32 2, [[BEAM]]
+; CHECK-NEXT:    [[IDXPROM:%.*]] = sext i32 [[MUL]] to i64
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[IDXPROM]]
+; CHECK-NEXT:    store i32 0, ptr [[ARRAYIDX]], align 4
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[MUL2:%.*]] = mul nsw i32 2, [[TMP1]]
+; CHECK-NEXT:    [[IDXPROM3:%.*]] = sext i32 [[MUL2]] to i64
+; CHECK-NEXT:    [[ARRAYIDX4:%.*]] = getelementptr inbounds i32, ptr [[TMP0]], i64 [[IDXPROM3]]
+; CHECK-NEXT:    store i32 1, ptr [[ARRAYIDX4]], align 4
+; CHECK-NEXT:    [[DOTPRE:%.*]] = load i32, ptr [[I]], align 4
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    [[TMP2:%.*]] = phi i32 [ [[DOTPRE]], [[IF_ELSE]] ], [ [[BEAM]], [[IF_THEN]] ]
+; CHECK-NEXT:    [[TMP3]] = phi ptr [ [[TMP0]], [[IF_ELSE]] ], [ [[A]], [[IF_THEN]] ]
+; CHECK-NEXT:    [[INC]] = add nsw i32 [[TMP2]], 1
+; CHECK-NEXT:    br label [[FOR_COND]]
+;
+entry:
+  %a.addr = alloca ptr, align 8
+  %beam.addr = alloca i32, align 4
+  %i = alloca i32, align 4
+  store ptr %a, ptr %a.addr, align 8
+  store i32 %beam, ptr %beam.addr, align 4
+  store i32 0, ptr %i, align 4
+  br label %for.cond
+
+for.cond:                                         ; preds = %if.end, %entry
+  %0 = phi ptr [ %3, %if.end ], [ %a, %entry ]
+  %1 = phi i32 [ %inc, %if.end ], [ 0, %entry ]
+  %cmp = icmp slt i32 %1, 10000
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond
+  ret void
+
+for.body:                                         ; preds = %for.cond
+  %cmp1 = icmp eq i32 %1, %beam
+  br i1 %cmp1, label %if.then, label %if.else
+
+if.then:                                          ; preds = %for.body
+  %mul = mul nsw i32 2, %beam
+  %idxprom = sext i32 %mul to i64
+  %arrayidx = getelementptr inbounds i32, ptr %a, i64 %idxprom
+  store i32 0, ptr %arrayidx, align 4
+  br label %if.end
+
+if.else:                                          ; preds = %for.body
+  %mul2 = mul nsw i32 2, %1
+  %idxprom3 = sext i32 %mul2 to i64
+  %arrayidx4 = getelementptr inbounds i32, ptr %0, i64 %idxprom3
+  store i32 1, ptr %arrayidx4, align 4
+  %.pre = load i32, ptr %i, align 4
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %2 = phi i32 [ %.pre, %if.else ], [ %beam, %if.then ]
+  %3 = phi ptr [ %0, %if.else ], [ %a, %if.then ]
+  %inc = add nsw i32 %2, 1
+  store i32 %inc, ptr %i, align 4
+  br label %for.cond
+}


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