Fix ExpandShiftWithUnknownAmountBit, which was completely bogus.

Pointed out by Javier Martinez (who also provided a patch).  Since
this logic is not used on (for example) x86, I guess nobody noticed.
Tested by generating SHL, SRL, SRA on various choices of i64 for all
possible shift amounts, and comparing with gcc.  Since I did this on
x86-32, I had to force the use of ExpandShiftWithUnknownAmountBit.
What I'm saying here is that I don't have a testcase I can add to the
repository.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90482 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 8ac8063be9ffee9ed8a5524cbb163352c0f59239..5599d25f6e3db651b96b6d7b75338213dbcdeee3 100644 (file)
--- a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -1167,55 +1167,56 @@ ExpandShiftWithUnknownAmountBit(SDNode *N, SDValue &Lo, SDValue &Hi) {
   GetExpandedInteger(N->getOperand(0), InL, InH);
 
   SDValue NVBitsNode = DAG.getConstant(NVTBits, ShTy);
-  SDValue Amt2 = DAG.getNode(ISD::SUB, dl, ShTy, NVBitsNode, Amt);
-  SDValue Cmp = DAG.getSetCC(dl, TLI.getSetCCResultType(ShTy),
-                             Amt, NVBitsNode, ISD::SETULT);
+  SDValue AmtExcess = DAG.getNode(ISD::SUB, dl, ShTy, Amt, NVBitsNode);
+  SDValue AmtLack = DAG.getNode(ISD::SUB, dl, ShTy, NVBitsNode, Amt);
+  SDValue isShort = DAG.getSetCC(dl, TLI.getSetCCResultType(ShTy),
+                                 Amt, NVBitsNode, ISD::SETULT);
 
-  SDValue Lo1, Hi1, Lo2, Hi2;
+  SDValue LoS, HiS, LoL, HiL;
   switch (N->getOpcode()) {
   default: llvm_unreachable("Unknown shift");
   case ISD::SHL:
-    // ShAmt < NVTBits
-    Lo1 = DAG.getConstant(0, NVT);                  // Low part is zero.
-    Hi1 = DAG.getNode(ISD::SHL, dl, NVT, InL, Amt); // High part from Lo part.
-
-    // ShAmt >= NVTBits
-    Lo2 = DAG.getNode(ISD::SHL, dl, NVT, InL, Amt);
-    Hi2 = DAG.getNode(ISD::OR, dl, NVT,
+    // Short: ShAmt < NVTBits
+    LoS = DAG.getNode(ISD::SHL, dl, NVT, InL, Amt);
+    HiS = DAG.getNode(ISD::OR, dl, NVT,
                       DAG.getNode(ISD::SHL, dl, NVT, InH, Amt),
-                      DAG.getNode(ISD::SRL, dl, NVT, InL, Amt2));
+                      DAG.getNode(ISD::SRL, dl, NVT, InL, AmtLack));
+
+    // Long: ShAmt >= NVTBits
+    LoL = DAG.getConstant(0, NVT);                        // Lo part is zero.
+    HiL = DAG.getNode(ISD::SHL, dl, NVT, InL, AmtExcess); // Hi from Lo part.
 
-    Lo = DAG.getNode(ISD::SELECT, dl, NVT, Cmp, Lo1, Lo2);
-    Hi = DAG.getNode(ISD::SELECT, dl, NVT, Cmp, Hi1, Hi2);
+    Lo = DAG.getNode(ISD::SELECT, dl, NVT, isShort, LoS, LoL);
+    Hi = DAG.getNode(ISD::SELECT, dl, NVT, isShort, HiS, HiL);
     return true;
   case ISD::SRL:
-    // ShAmt < NVTBits
-    Hi1 = DAG.getConstant(0, NVT);                  // Hi part is zero.
-    Lo1 = DAG.getNode(ISD::SRL, dl, NVT, InH, Amt); // Lo part from Hi part.
-
-    // ShAmt >= NVTBits
-    Hi2 = DAG.getNode(ISD::SRL, dl, NVT, InH, Amt);
-    Lo2 = DAG.getNode(ISD::OR, dl, NVT,
-                     DAG.getNode(ISD::SRL, dl, NVT, InL, Amt),
-                     DAG.getNode(ISD::SHL, dl, NVT, InH, Amt2));
-
-    Lo = DAG.getNode(ISD::SELECT, dl, NVT, Cmp, Lo1, Lo2);
-    Hi = DAG.getNode(ISD::SELECT, dl, NVT, Cmp, Hi1, Hi2);
+    // Short: ShAmt < NVTBits
+    HiS = DAG.getNode(ISD::SRL, dl, NVT, InH, Amt);
+    LoS = DAG.getNode(ISD::OR, dl, NVT,
+                      DAG.getNode(ISD::SRL, dl, NVT, InL, Amt),
+                      DAG.getNode(ISD::SHL, dl, NVT, InH, AmtLack));
+
+    // Long: ShAmt >= NVTBits
+    HiL = DAG.getConstant(0, NVT);                        // Hi part is zero.
+    LoL = DAG.getNode(ISD::SRL, dl, NVT, InH, AmtExcess); // Lo from Hi part.
+
+    Lo = DAG.getNode(ISD::SELECT, dl, NVT, isShort, LoS, LoL);
+    Hi = DAG.getNode(ISD::SELECT, dl, NVT, isShort, HiS, HiL);
     return true;
   case ISD::SRA:
-    // ShAmt < NVTBits
-    Hi1 = DAG.getNode(ISD::SRA, dl, NVT, InH,       // Sign extend high part.
-                       DAG.getConstant(NVTBits-1, ShTy));
-    Lo1 = DAG.getNode(ISD::SRA, dl, NVT, InH, Amt); // Lo part from Hi part.
-
-    // ShAmt >= NVTBits
-    Hi2 = DAG.getNode(ISD::SRA, dl, NVT, InH, Amt);
-    Lo2 = DAG.getNode(ISD::OR, dl, NVT,
+    // Short: ShAmt < NVTBits
+    HiS = DAG.getNode(ISD::SRA, dl, NVT, InH, Amt);
+    LoS = DAG.getNode(ISD::OR, dl, NVT,
                       DAG.getNode(ISD::SRL, dl, NVT, InL, Amt),
-                      DAG.getNode(ISD::SHL, dl, NVT, InH, Amt2));
+                      DAG.getNode(ISD::SHL, dl, NVT, InH, AmtLack));
+
+    // Long: ShAmt >= NVTBits
+    HiL = DAG.getNode(ISD::SRA, dl, NVT, InH,             // Sign of Hi part.
+                      DAG.getConstant(NVTBits-1, ShTy));
+    LoL = DAG.getNode(ISD::SRA, dl, NVT, InH, AmtExcess); // Lo from Hi part.
 
-    Lo = DAG.getNode(ISD::SELECT, dl, NVT, Cmp, Lo1, Lo2);
-    Hi = DAG.getNode(ISD::SELECT, dl, NVT, Cmp, Hi1, Hi2);
+    Lo = DAG.getNode(ISD::SELECT, dl, NVT, isShort, LoS, LoL);
+    Hi = DAG.getNode(ISD::SELECT, dl, NVT, isShort, HiS, HiL);
     return true;
   }