[committed, amdgcn] Fix stack initialization bug

[committed, amdgcn] Fix stack initialization bug

[Andrew Stubbs]

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This patch fixes a 64-bit arithmetic bug in which the wrong instruction 
was used for the lo-part resulting in an incorrect calculation for the 
hi-part (signed vs. unsigned add). This causes a Memory Access Fault 
whenever the launcher happens to choose a problematic address for the 
stack allocation.

This problem never occurred on GCN3 because the launcher always chose 
addresses in the 32-bit range. It seems to happen more frequently on 
GCN5 devices since a recent ROCm update.

-- 
Andrew Stubbs
Mentor Graphics / CodeSourcery

[-- Attachment #2: 190524-prologue-add.patch --]
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Fix 64-bit addition in prologue.

2019-05-24  Andrew Stubbs  <ams@codesourcery.com>

	gcc/
	* config/gcn/gcn.c (gcn_expand_prologue): Use gen_addsi3_scalar_carry
	for lo-part.

diff --git a/gcc/config/gcn/gcn.c b/gcc/config/gcn/gcn.c
index 47630c6edb4..71f4b4ce35a 100644
--- a/gcc/config/gcn/gcn.c
+++ b/gcc/config/gcn/gcn.c
@@ -2824,9 +2824,9 @@ gcn_expand_prologue ()
       emit_move_insn (fp_lo, gen_rtx_REG (SImode, 0));
       emit_insn (gen_andsi3_scc (fp_hi, gen_rtx_REG (SImode, 1),
 				 gen_int_mode (0xffff, SImode)));
-      emit_insn (gen_addsi3_scc (fp_lo, fp_lo, wave_offset));
-      emit_insn (gen_addcsi3_scalar_zero (fp_hi, fp_hi,
-					  gen_rtx_REG (BImode, SCC_REG)));
+      rtx scc = gen_rtx_REG (BImode, SCC_REG);
+      emit_insn (gen_addsi3_scalar_carry (fp_lo, fp_lo, wave_offset, scc));
+      emit_insn (gen_addcsi3_scalar_zero (fp_hi, fp_hi, scc));
 
       if (sp_adjust > 0)
 	emit_insn (gen_adddi3_scc (sp, fp, gen_int_mode (sp_adjust, DImode)));

Re: [committed, amdgcn] Fix stack initialization bug

[Andrew Stubbs]

On 24/05/2019 12:12, Andrew Stubbs wrote:
> This patch fixes a 64-bit arithmetic bug in which the wrong instruction 
> was used for the lo-part resulting in an incorrect calculation for the 
> hi-part (signed vs. unsigned add). This causes a Memory Access Fault 
> whenever the launcher happens to choose a problematic address for the 
> stack allocation.
> 
> This problem never occurred on GCN3 because the launcher always chose 
> addresses in the 32-bit range. It seems to happen more frequently on 
> GCN5 devices since a recent ROCm update.

Now backported to gcc-9-branch.

Andrew