[indvars] Fix pointer IV expand type in genLoopLimit

[wenju]

Summary

This fixes a regression in 0766c1bd5c0e and restores the expand type
of pointer IV to before the commit.

[nikic]

Please update the patch description to clarify what the "regression" was (does it crash? does it miscompile? does it produce suboptimal code?) and how this fixes it.

Please also minimize the test case (do we need that huge global? etc), convert it to use opaque pointers and use update_test_checks.py.

[wenju]

The regression was an assert failure in IndVarSimplifyPass. The LIT is over-simplified and doesn't have the assert.
I just find out that the regression only exists in non-opaque-pointer mode. So this fix is not needed.
Sorry for the noise. I should have tested the opaque pointer mode.

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

if (IndVar->getType()->isIntegerTy() &&
     if (!isa<SCEVConstant>(IVInit) || !isa<SCEVConstant>(ExitCount))
       AR = cast<SCEVAddRecExpr>(SE->getTruncateExpr(AR, ExitCount->getType()));
   }
 
   const SCEVAddRecExpr *ARBase = UsePostInc ? AR->getPostIncExpr(*SE) : AR;
   const SCEV *IVLimit = ARBase->evaluateAtIteration(ExitCount, *SE);
   assert(SE->isLoopInvariant(IVLimit, L) &&
          "Computed iteration count is not loop invariant!");
-  return Rewriter.expandCodeFor(IVLimit, ARBase->getType(),
-                                ExitingBB->getTerminator());
+  auto *ExpandTy =
+      IndVar->getType()->isPointerTy() ? IndVar->getType() : ARBase->getType();
+  return Rewriter.expandCodeFor(IVLimit, ExpandTy, ExitingBB->getTerminator());
 }
 
 /// This method rewrites the exit condition of the loop to be a canonical !=
 /// comparison against the incremented loop induction variable.  This pass is
 /// able to rewrite the exit tests of any loop where the SCEV analysis can
 /// determine a loop-invariant trip count of the loop, which is actually a much
 /// broader range than just linear tests.
 bool IndVarSimplify::

llvm/test/Transforms/IndVarSimplify/looplimit-pointer-type.ll

+; RUN: opt %s -passes=indvars -S | FileCheck %s
+
+; Check the case SCEV base pointer type isn't the same as indvar pointer type.
+
+; CHECK-NOT: %wstr.addr = phi
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+@.str.1 = internal addrspace(1) constant [93 x i16] [i16 68, i16 58, i16 92, i16 105, i16 117, i16 115, i16 101, i16 114, i16 115, i16 92, i16 119, i16 101, i16 110, i16 106, i16 117, i16 104, i16 101, i16 92, i16 119, i16 115, i16 92, i16 120, i16 45, i16 119, i16 101, i16 98, i16 92, i16 100, i16 101, i16 112, i16 108, i16 111, i16 121, i16 92, i16 119, i16 105, i16 110, i16 95, i16 112, i16 114, i16 111, i16 100, i16 92, i16 98, i16 105, i16 110, i16 45, i16 108, i16 108, i16 118, i16 109, i16 92, i16 46, i16 46, i16 92, i16 105, i16 110, i16 99, i16 108, i16 117, i16 100, i16 101, i16 92, i16 115, i16 121, i16 99, i16 108, i16 47, i16 101, i16 120, i16 116, i16 47, i16 111, i16 110, i16 101, i16 97, i16 112, i16 105, i16 47, i16 115, i16 117, i16 98, i16 95, i16 103, i16 114, i16 111, i16 117, i16 112, i16 46, i16 104, i16 112, i16 112, i16 0]
+
+define void @test() {
+entry:
+  %0 = getelementptr [256 x i8], [256 x i8]* null, i64 0, i64 0
+  br label %while.body
+
+while.body:                                   ; preds = %while.body, %entry
+  %str.addr = phi i8* [ %0, %entry ], [ %incdec.ptr7, %while.body ]
+  %wstr.addr = phi i16 addrspace(4)* [ addrspacecast (i16 addrspace(1)* getelementptr inbounds ([93 x i16], [93 x i16] addrspace(1)* @.str.1, i64 0, i64 0) to i16 addrspace(4)*), %entry ], [ %incdec.ptr, %while.body ]
+  %incdec.ptr = getelementptr i16, i16 addrspace(4)* %wstr.addr, i64 1
+  %incdec.ptr7 = getelementptr i8, i8* %str.addr, i64 1
+  store i8 0, i8* %str.addr, align 1
+  %1 = load i16, i16 addrspace(4)* %wstr.addr, align 2
+  %cmp1.not.i.i = icmp eq i16 %1, 0
+  br i1 %cmp1.not.i.i, label %exit, label %while.body
+
+exit:      ; preds = %while.body
+  ret void
+}