Fix codegen to compute the size of an allocation by multiplying the

size by the array amount as an i32 value instead of promoting from
i32 to i64 then doing the multiply.  Not doing this broke wrap-around
assumptions that the optimizers (validly) made.  The ultimate real
fix for this is to introduce i64 version of alloca and remove mallocinst.

This fixes PR3829

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67093 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index 0dbc35b2248daeb08d10f92624153c9f406e8521..855f9a443b757aaefae12542dd9a28b1e21ca969 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -2763,6 +2763,13 @@ void SelectionDAGLowering::visitAlloca(AllocaInst &I) {
              I.getAlignment());
 
   SDValue AllocSize = getValue(I.getArraySize());
+  
+  AllocSize = DAG.getNode(ISD::MUL, getCurDebugLoc(), AllocSize.getValueType(),
+                          AllocSize,
+                          DAG.getConstant(TySize, AllocSize.getValueType()));
+  
+  
+  
   MVT IntPtr = TLI.getPointerTy();
   if (IntPtr.bitsLT(AllocSize.getValueType()))
     AllocSize = DAG.getNode(ISD::TRUNCATE, getCurDebugLoc(),
@@ -2771,9 +2778,6 @@ void SelectionDAGLowering::visitAlloca(AllocaInst &I) {
     AllocSize = DAG.getNode(ISD::ZERO_EXTEND, getCurDebugLoc(),
                             IntPtr, AllocSize);
 
-  AllocSize = DAG.getNode(ISD::MUL, getCurDebugLoc(), IntPtr, AllocSize,
-                          DAG.getIntPtrConstant(TySize));
-
   // Handle alignment.  If the requested alignment is less than or equal to
   // the stack alignment, ignore it.  If the size is greater than or equal to
   // the stack alignment, we note this in the DYNAMIC_STACKALLOC node.
@@ -5425,6 +5429,16 @@ void SelectionDAGLowering::visitInlineAsm(CallSite CS) {
 void SelectionDAGLowering::visitMalloc(MallocInst &I) {
   SDValue Src = getValue(I.getOperand(0));
 
+  // Scale up by the type size in the original i32 type width.  Various
+  // mid-level optimizers may make assumptions about demanded bits etc from the
+  // i32-ness of the optimizer: we do not want to promote to i64 and then
+  // multiply on 64-bit targets.
+  // FIXME: Malloc inst should go away: PR715.
+  uint64_t ElementSize = TD->getTypePaddedSize(I.getType()->getElementType());
+  if (ElementSize != 1)
+    Src = DAG.getNode(ISD::MUL, getCurDebugLoc(), Src.getValueType(),
+                      Src, DAG.getConstant(ElementSize, Src.getValueType()));
+  
   MVT IntPtr = TLI.getPointerTy();
 
   if (IntPtr.bitsLT(Src.getValueType()))
@@ -5432,11 +5446,6 @@ void SelectionDAGLowering::visitMalloc(MallocInst &I) {
   else if (IntPtr.bitsGT(Src.getValueType()))
     Src = DAG.getNode(ISD::ZERO_EXTEND, getCurDebugLoc(), IntPtr, Src);
 
-  // Scale the source by the type size.
-  uint64_t ElementSize = TD->getTypePaddedSize(I.getType()->getElementType());
-  Src = DAG.getNode(ISD::MUL, getCurDebugLoc(), Src.getValueType(),
-                    Src, DAG.getIntPtrConstant(ElementSize));
-
   TargetLowering::ArgListTy Args;
   TargetLowering::ArgListEntry Entry;
   Entry.Node = Src;

diff --git a/test/CodeGen/X86/x86-64-malloc.ll b/test/CodeGen/X86/x86-64-malloc.ll
new file mode 100644 (file)
index 0000000..4beb5c2
--- /dev/null
+++ b/test/CodeGen/X86/x86-64-malloc.ll
@@ -0,0 +1,10 @@
+; RUN: llvm-as < %s | llc -march=x86-64 | grep {shll.*3, %edi}
+; PR3829
+; The generated code should multiply by 3 (sizeof i8*) as an i32,
+; not as an i64!
+
+define i8** @test(i32 %sz) {
+       %sub = add i32 %sz, 536870911           ; <i32> [#uses=1]
+       %call = malloc i8*, i32 %sub            ; <i8**> [#uses=1]
+       ret i8** %call
+}