[llvm] r298882 - [LV] Transform truncations of non-primary induction variables

[Matthew Simpson via llvm-commits]

Author: mssimpso
Date: Mon Mar 27 15:07:38 2017
New Revision: 298882

URL: http://llvm.org/viewvc/llvm-project?rev=298882&view=rev
Log:
[LV] Transform truncations of non-primary induction variables

The vectorizer tries to replace truncations of induction variables with new
induction variables having the smaller type. After r295063, this optimization
was applied to all integer induction variables, including non-primary ones.
When optimizing the truncation of a non-primary induction variable, we still
need to transform the new induction so that it has the correct start value.
This should fix PR32419.

Reference: https://bugs.llvm.org/show_bug.cgi?id=32419

Modified:
    llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/trunk/test/Transforms/LoopVectorize/induction.ll

Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=298882&r1=298881&r2=298882&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Mon Mar 27 15:07:38 2017
@@ -2521,22 +2521,21 @@ void InnerLoopVectorizer::widenIntOrFpIn
   // induction variable and step. Otherwise, derive these values from the
   // induction descriptor.
   if (!VectorizedIV || NeedsScalarIV) {
+    ScalarIV = Induction;
+    if (IV != OldInduction) {
+      ScalarIV = IV->getType()->isIntegerTy()
+                     ? Builder.CreateSExtOrTrunc(Induction, IV->getType())
+                     : Builder.CreateCast(Instruction::SIToFP, Induction,
+                                          IV->getType());
+      ScalarIV = ID.transform(Builder, ScalarIV, PSE.getSE(), DL);
+      ScalarIV->setName("offset.idx");
+    }
     if (Trunc) {
       auto *TruncType = cast<IntegerType>(Trunc->getType());
       assert(Step->getType()->isIntegerTy() &&
              "Truncation requires an integer step");
-      ScalarIV = Builder.CreateCast(Instruction::Trunc, Induction, TruncType);
+      ScalarIV = Builder.CreateTrunc(ScalarIV, TruncType);
       Step = Builder.CreateTrunc(Step, TruncType);
-    } else {
-      ScalarIV = Induction;
-      if (IV != OldInduction) {
-        ScalarIV = IV->getType()->isIntegerTy()
-                       ? Builder.CreateSExtOrTrunc(ScalarIV, IV->getType())
-                       : Builder.CreateCast(Instruction::SIToFP, Induction,
-                                            IV->getType());
-        ScalarIV = ID.transform(Builder, ScalarIV, PSE.getSE(), DL);
-        ScalarIV->setName("offset.idx");
-      }
     }
   }
 

Modified: llvm/trunk/test/Transforms/LoopVectorize/induction.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/induction.ll?rev=298882&r1=298881&r2=298882&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/induction.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/induction.ll Mon Mar 27 15:07:38 2017
@@ -804,3 +804,48 @@ for.body:
 for.end:
   ret void
 }
+
+; PR32419. Ensure we transform truncated non-primary induction variables. In
+; the test case below we replace %tmp1 with a new induction variable. Because
+; the truncated value is non-primary, we must compute an offset from the
+; primary induction variable.
+;
+; CHECK-LABEL: @PR32419(
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, %vector.ph ], [ [[INDEX_NEXT:%.*]], %[[PRED_UREM_CONTINUE4:.*]] ]
+; CHECK:         [[OFFSET_IDX:%.*]] = add i32 -20, [[INDEX]]
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc i32 [[OFFSET_IDX]] to i16
+; CHECK:         [[TMP8:%.*]] = add i16 [[TMP1]], 0
+; CHECK-NEXT:    [[TMP9:%.*]] = urem i16 %b, [[TMP8]]
+; CHECK:         [[TMP15:%.*]] = add i16 [[TMP1]], 1
+; CHECK-NEXT:    [[TMP16:%.*]] = urem i16 %b, [[TMP15]]
+; CHECK:       [[PRED_UREM_CONTINUE4]]:
+; CHECK:         br i1 {{.*}}, label %middle.block, label %vector.body
+;
+define i32 @PR32419(i32 %a, i16 %b) {
+entry:
+  br label %for.body
+
+for.body:
+  %i = phi i32 [ -20, %entry ], [ %i.next, %for.inc ]
+  %tmp0 = phi i32 [ %a, %entry ], [ %tmp6, %for.inc ]
+  %tmp1 = trunc i32 %i to i16
+  %tmp2 = icmp eq i16 %tmp1, 0
+  br i1 %tmp2, label %for.inc, label %for.cond
+
+for.cond:
+  %tmp3 = urem i16 %b, %tmp1
+  br label %for.inc
+
+for.inc:
+  %tmp4 = phi i16 [ %tmp3, %for.cond ], [ 0, %for.body ]
+  %tmp5 = sext i16 %tmp4 to i32
+  %tmp6 = or i32 %tmp0, %tmp5
+  %i.next = add nsw i32 %i, 1
+  %cond = icmp eq i32 %i.next, 0
+  br i1 %cond, label %for.end, label %for.body
+
+for.end:
+  %tmp7 = phi i32 [ %tmp6, %for.inc ]
+  ret i32 %tmp7
+}