[llvm] r217800 - [CodeGenPrepare][AddressingModeMatcher] Fix a think-o for the sext(zext) -> zext promotion

[Quentin Colombet]

Author: qcolombet
Date: Mon Sep 15 13:26:58 2014
New Revision: 217800

URL: http://llvm.org/viewvc/llvm-project?rev=217800&view=rev
Log:
[CodeGenPrepare][AddressingModeMatcher] Fix a think-o for the sext(zext) -> zext promotion
introduced in r217629.
We were returning the old sext instead of the new zext as the promoted instruction!

Thanks Joerg Sonnenberger for the test case.

Modified:
    llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
    llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll

Modified: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp?rev=217800&r1=217799&r2=217800&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp Mon Sep 15 13:26:58 2014
@@ -1849,6 +1849,7 @@ Value *TypePromotionHelper::promoteOpera
   // By construction, the operand of SExt is an instruction. Otherwise we cannot
   // get through it and this method should not be called.
   Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
+  Instruction *ExtInst = SExt;
   if (isa<ZExtInst>(SExtOpnd)) {
     // Replace sext(zext(opnd))
     // => zext(opnd).
@@ -1856,6 +1857,7 @@ Value *TypePromotionHelper::promoteOpera
         TPT.createZExt(SExt, SExtOpnd->getOperand(0), SExt->getType());
     TPT.replaceAllUsesWith(SExt, ZExt);
     TPT.eraseInstruction(SExt);
+    ExtInst = ZExt;
   } else {
     // Replace sext(trunc(opnd)) or sext(sext(opnd))
     // => sext(opnd).
@@ -1867,14 +1869,14 @@ Value *TypePromotionHelper::promoteOpera
   if (SExtOpnd->use_empty())
     TPT.eraseInstruction(SExtOpnd);
 
-  // Check if the sext is still needed.
-  if (SExt->getType() != SExt->getOperand(0)->getType())
-    return SExt;
+  // Check if the extension is still needed.
+  if (ExtInst->getType() != ExtInst->getOperand(0)->getType())
+    return ExtInst;
 
-  // At this point we have: sext ty opnd to ty.
-  // Reassign the uses of SExt to the opnd and remove SExt.
-  Value *NextVal = SExt->getOperand(0);
-  TPT.eraseInstruction(SExt, NextVal);
+  // At this point we have: ext ty opnd to ty.
+  // Reassign the uses of ExtInst to the opnd and remove ExtInst.
+  Value *NextVal = ExtInst->getOperand(0);
+  TPT.eraseInstruction(ExtInst, NextVal);
   return NextVal;
 }
 

Modified: llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll?rev=217800&r1=217799&r2=217800&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll (original)
+++ llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll Mon Sep 15 13:26:58 2014
@@ -336,3 +336,66 @@ end:
   %final = load i32* %addr
   ret i32 %final
 }
+
+%struct.dns_packet = type { i32, i32, %union.anon }
+%union.anon = type { i32 }
+
+ at a = common global i32 0, align 4
+ at b = common global i16 0, align 2
+
+; We used to crash on this function because we did not return the right
+; promoted instruction for %conv.i.
+; Make sure we generate the right code now.
+; CHECK-LABEL: @fn3
+; %conv.i is used twice and only one of its use is being promoted.
+; Use it at the starting point for the matching.
+; CHECK: %conv.i = zext i16 [[PLAIN_OPND:%[.a-zA-Z_0-9-]+]] to i32
+; CHECK-NEXT: [[PROMOTED_CONV:%[.a-zA-Z_0-9-]+]] = zext i16 [[PLAIN_OPND]] to i64
+; CHECK-NEXT: [[BASE:%[a-zA-Z_0-9-]+]] = ptrtoint %struct.dns_packet* %P to i64
+; CHECK-NEXT: [[ADD:%[a-zA-Z_0-9-]+]] = add i64 [[BASE]], [[PROMOTED_CONV]]
+; CHECK-NEXT: [[ADDR:%[a-zA-Z_0-9-]+]] = add i64 [[ADD]], 7
+; CHECK-NEXT: [[CAST:%[a-zA-Z_0-9-]+]] = inttoptr i64 [[ADDR]] to i8*
+; CHECK-NEXT: load i8* [[CAST]], align 1
+define signext i16 @fn3(%struct.dns_packet* nocapture readonly %P) {
+entry:
+  %tmp = getelementptr inbounds %struct.dns_packet* %P, i64 0, i32 2
+  %data.i.i = bitcast %union.anon* %tmp to [0 x i8]*
+  br label %while.body.i.i
+
+while.body.i.i:                                   ; preds = %while.body.i.i, %entry
+  %src.addr.0.i.i = phi i16 [ 0, %entry ], [ %inc.i.i, %while.body.i.i ]
+  %inc.i.i = add i16 %src.addr.0.i.i, 1
+  %idxprom.i.i = sext i16 %src.addr.0.i.i to i64
+  %arrayidx.i.i = getelementptr inbounds [0 x i8]* %data.i.i, i64 0, i64 %idxprom.i.i
+  %tmp1 = load i8* %arrayidx.i.i, align 1
+  %conv2.i.i = zext i8 %tmp1 to i32
+  %and.i.i = and i32 %conv2.i.i, 15
+  store i32 %and.i.i, i32* @a, align 4
+  %tobool.i.i = icmp eq i32 %and.i.i, 0
+  br i1 %tobool.i.i, label %while.body.i.i, label %fn1.exit.i
+
+fn1.exit.i:                                       ; preds = %while.body.i.i
+  %inc.i.i.lcssa = phi i16 [ %inc.i.i, %while.body.i.i ]
+  %conv.i = zext i16 %inc.i.i.lcssa to i32
+  %sub.i = add nsw i32 %conv.i, -1
+  %idxprom.i = sext i32 %sub.i to i64
+  %arrayidx.i = getelementptr inbounds [0 x i8]* %data.i.i, i64 0, i64 %idxprom.i
+  %tmp2 = load i8* %arrayidx.i, align 1
+  %conv2.i = sext i8 %tmp2 to i16
+  store i16 %conv2.i, i16* @b, align 2
+  %sub4.i = sub nsw i32 0, %conv.i
+  %conv5.i = zext i16 %conv2.i to i32
+  %cmp.i = icmp sgt i32 %conv5.i, %sub4.i
+  br i1 %cmp.i, label %if.then.i, label %fn2.exit
+
+if.then.i:                                        ; preds = %fn1.exit.i
+  %end.i = getelementptr inbounds %struct.dns_packet* %P, i64 0, i32 1
+  %tmp3 = load i32* %end.i, align 4
+  %sub7.i = add i32 %tmp3, 65535
+  %conv8.i = trunc i32 %sub7.i to i16
+  br label %fn2.exit
+
+fn2.exit:                                         ; preds = %if.then.i, %fn1.exit.i
+  %retval.0.i = phi i16 [ %conv8.i, %if.then.i ], [ undef, %fn1.exit.i ]
+  ret i16 %retval.0.i
+}