On 19.11.2015 03:55, Tom Stellard wrote:
On Thu, Nov 19, 2015 at 11:31:55AM +0900, Michel Dänzer wrote:
From: Michel Dänzer <michel.daen...@amd.com>
llvm.exp2.f32 doesn't work in some cases yet.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92709
Signed-off-by: Michel Dänzer <michel.daen...@amd.com>
---
Once the problem is fixed in the LLVM AMDGPU backend, we can re-enable
llvm.exp2.f32 for the fixed LLVM version.
src/gallium/drivers/radeon/radeon_setup_tgsi_llvm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/gallium/drivers/radeon/radeon_setup_tgsi_llvm.c
b/src/gallium/drivers/radeon/radeon_setup_tgsi_llvm.c
index ac99e73..c94f109 100644
--- a/src/gallium/drivers/radeon/radeon_setup_tgsi_llvm.c
+++ b/src/gallium/drivers/radeon/radeon_setup_tgsi_llvm.c
@@ -1539,7 +1539,7 @@ void radeon_llvm_context_init(struct radeon_llvm_context
* ctx)
bld_base->op_actions[TGSI_OPCODE_ENDIF].emit = endif_emit;
bld_base->op_actions[TGSI_OPCODE_ENDLOOP].emit = endloop_emit;
bld_base->op_actions[TGSI_OPCODE_EX2].emit = build_tgsi_intrinsic_nomem;
- bld_base->op_actions[TGSI_OPCODE_EX2].intr_name = "llvm.exp2.f32";
+ bld_base->op_actions[TGSI_OPCODE_EX2].intr_name = "llvm.AMDIL.exp.";
Do we want a native instruction here, or do we want IEEE precise exp2?
If it's the former then we shouldn't be using llvm.exp2.f32 anyway.
I know that we need to use llvm.AMDIL.exp. for older LLVM, but for newer
LLVM, I would really like to start doing intrinsics the correct way. In
this case, it means adding an llvm.amdgcn.exp.f32 intrinsic to
include/llvm/IR/IntrinsicsAMDGPU.td. In the section with the amdgcn
TargetPrefix.
Doesn't AMDGPU currently emit native instructions for the various math
intrinsics anyway? If your plan is to change that and we add our own
intrinsics, what's the plan to still benefit from existing LLVM
optimization passes?
FWIW, the original bug that Michel addresses here is caused by LLVM
libcall optimizations replacing the exp2 _intrinsic_ by a ldexp
_libcall_, which AMDGPU codegen cannot deal with. I suggested to address
this with http://reviews.llvm.org/D14327. Could you take a look at that?
Cheers,
Nicolai
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