[PATCH] D17872: [NVPTX] Add a truncate DAG node to some calls.

[Justin Lebar via llvm-commits]

jlebar created this revision.
jlebar added a reviewer: jingyue.
jlebar added subscribers: jholewinski, tra, llvm-commits.

Previously, we were running afoul of the assertion

  EVT(CLI.Ins[i].VT) == InVals[i].getValueType() && "LowerCall emitted a value with the wrong type!"

in SelectionDAGBuilder.cpp when running the NVPTX/i8-param.ll test.
This is because our backend (for some reason) treats small return values
as i32, but it wasn't ever truncating the i32 back down to the expected
width in the DAG.

Unclear to me whether this fixes any actual bugs -- in this test, at
least, the generated code is unchanged.

http://reviews.llvm.org/D17872

Files:
  lib/Target/NVPTX/NVPTXISelLowering.cpp

Index: lib/Target/NVPTX/NVPTXISelLowering.cpp
===================================================================
--- lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -1620,17 +1620,20 @@
       for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
         unsigned sz = VTs[i].getSizeInBits();
         unsigned AlignI = GreatestCommonDivisor64(RetAlign, Offsets[i]);
-        bool needTruncate = sz < 8;
-        if (VTs[i].isInteger() && (sz < 8))
+        bool needTruncate = false;
+        if (VTs[i].isInteger() && sz < 8) {
           sz = 8;
+          needTruncate = true;
+        }
 
         SmallVector<EVT, 4> LoadRetVTs;
         EVT TheLoadType = VTs[i];
         if (retTy->isIntegerTy() && DL.getTypeAllocSizeInBits(retTy) < 32) {
           // This is for integer types only, and specifically not for
           // aggregates.
           LoadRetVTs.push_back(MVT::i32);
           TheLoadType = MVT::i32;
+          needTruncate = true;
         } else if (sz < 16) {
           // If loading i1/i8 result, generate
           //   load i8 (-> i16)


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