gallivm: work around LLVM 2.6 bug when calling C functions

Create a constant int pointer to the C function, then cast it to the
function's type.  This avoids using trampoline code which seem to be
inadvertantly freed by LLVM in some situations (which leads to segfaults).
The root issue and work-around were found by José.

NOTE: This is a candidate for the 7.10 branch

1 files changed, 18 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_const.h b/src/gallium/auxiliary/gallivm/lp_bld_const.h
index c749a7a315..680211fbbd 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_const.h
+++ b/src/gallium/auxiliary/gallivm/lp_bld_const.h
@@ -125,4 +125,22 @@ lp_build_const_float(struct gallivm_state *gallivm, float x)
 }
 
 
+/** Return constant-valued pointer to int */
+static INLINE LLVMValueRef
+lp_build_const_int_pointer(struct gallivm_state *gallivm, const void *ptr)
+{
+   LLVMTypeRef int_type;
+   LLVMValueRef v;
+
+   /* int type large enough to hold a pointer */
+   int_type = LLVMIntTypeInContext(gallivm->context, 8 * sizeof(void *));
+   v = LLVMConstInt(int_type, (unsigned long long) ptr, 0);
+   v = LLVMBuildIntToPtr(gallivm->builder, v,
+                         LLVMPointerType(int_type, 0),
+                         "cast int to ptr");
+   return v;
+}
+
+
+
 #endif /* !LP_BLD_CONST_H */