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authorRoland Scheidegger <[email protected]>2013-07-30 21:26:27 +0200
committerRoland Scheidegger <[email protected]>2013-08-02 03:49:57 +0200
commite7ed70a52e2d0efc11d1e9fe19938bc431f947c1 (patch)
tree3e1a5cb36d282047bebd91807540812a47656191 /src
parent7a72bef47e8731276ac4ca0b8c4d6d50366c1ec2 (diff)
gallivm: obey clarified shift behavior
llvm shifts are undefined for shift counts exceeding (or matching) bit width, so need to apply a mask for the tgsi shift instructions. v2: only use mask for the tgsi shift instructions, not for the build shift helpers. None of the internal callers need this behavior, and while llvm can optimize away the masking for constants there are legitimate cases where it might not be able to do so even if we know that shift count must be smaller than type width (currently all such callers do not use the build shift helpers). Reviewed-by: Zack Rusin <[email protected]> Reviewed-by: Jose Fonseca <[email protected]>
Diffstat (limited to 'src')
-rw-r--r--src/gallium/auxiliary/gallivm/lp_bld_bitarit.c8
-rw-r--r--src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c24
2 files changed, 24 insertions, 8 deletions
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_bitarit.c b/src/gallium/auxiliary/gallivm/lp_bld_bitarit.c
index 97ae1622c27..9892d7aa2b8 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_bitarit.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_bitarit.c
@@ -168,6 +168,7 @@ lp_build_not(struct lp_build_context *bld, LLVMValueRef a)
/**
* Shift left.
+ * Result is undefined if the shift count is not smaller than the type width.
*/
LLVMValueRef
lp_build_shl(struct lp_build_context *bld, LLVMValueRef a, LLVMValueRef b)
@@ -189,6 +190,7 @@ lp_build_shl(struct lp_build_context *bld, LLVMValueRef a, LLVMValueRef b)
/**
* Shift right.
+ * Result is undefined if the shift count is not smaller than the type width.
*/
LLVMValueRef
lp_build_shr(struct lp_build_context *bld, LLVMValueRef a, LLVMValueRef b)
@@ -214,23 +216,25 @@ lp_build_shr(struct lp_build_context *bld, LLVMValueRef a, LLVMValueRef b)
/**
* Shift left with immediate.
+ * The immediate shift count must be smaller than the type width.
*/
LLVMValueRef
lp_build_shl_imm(struct lp_build_context *bld, LLVMValueRef a, unsigned imm)
{
LLVMValueRef b = lp_build_const_int_vec(bld->gallivm, bld->type, imm);
- assert(imm <= bld->type.width);
+ assert(imm < bld->type.width);
return lp_build_shl(bld, a, b);
}
/**
* Shift right with immediate.
+ * The immediate shift count must be smaller than the type width.
*/
LLVMValueRef
lp_build_shr_imm(struct lp_build_context *bld, LLVMValueRef a, unsigned imm)
{
LLVMValueRef b = lp_build_const_int_vec(bld->gallivm, bld->type, imm);
- assert(imm <= bld->type.width);
+ assert(imm < bld->type.width);
return lp_build_shr(bld, a, b);
}
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
index d16ccae37fb..f46166101da 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
@@ -1203,8 +1203,12 @@ ishr_emit_cpu(
struct lp_build_tgsi_context * bld_base,
struct lp_build_emit_data * emit_data)
{
- emit_data->output[emit_data->chan] = lp_build_shr(&bld_base->int_bld,
- emit_data->args[0], emit_data->args[1]);
+ struct lp_build_context *int_bld = &bld_base->int_bld;
+ LLVMValueRef mask = lp_build_const_vec(int_bld->gallivm, int_bld->type,
+ int_bld->type.width - 1);
+ LLVMValueRef masked_count = lp_build_and(int_bld, emit_data->args[1], mask);
+ emit_data->output[emit_data->chan] = lp_build_shr(int_bld, emit_data->args[0],
+ masked_count);
}
/* TGSI_OPCODE_ISLT (CPU Only) */
@@ -1439,8 +1443,12 @@ shl_emit_cpu(
struct lp_build_tgsi_context * bld_base,
struct lp_build_emit_data * emit_data)
{
- emit_data->output[emit_data->chan] = lp_build_shl(&bld_base->uint_bld,
- emit_data->args[0], emit_data->args[1]);
+ struct lp_build_context *uint_bld = &bld_base->uint_bld;
+ LLVMValueRef mask = lp_build_const_vec(uint_bld->gallivm, uint_bld->type,
+ uint_bld->type.width - 1);
+ LLVMValueRef masked_count = lp_build_and(uint_bld, emit_data->args[1], mask);
+ emit_data->output[emit_data->chan] = lp_build_shl(uint_bld, emit_data->args[0],
+ masked_count);
}
/* TGSI_OPCODE_SIN (CPU Only) */
@@ -1647,8 +1655,12 @@ ushr_emit_cpu(
struct lp_build_tgsi_context * bld_base,
struct lp_build_emit_data * emit_data)
{
- emit_data->output[emit_data->chan] = lp_build_shr(&bld_base->uint_bld,
- emit_data->args[0], emit_data->args[1]);
+ struct lp_build_context *uint_bld = &bld_base->uint_bld;
+ LLVMValueRef mask = lp_build_const_vec(uint_bld->gallivm, uint_bld->type,
+ uint_bld->type.width - 1);
+ LLVMValueRef masked_count = lp_build_and(uint_bld, emit_data->args[1], mask);
+ emit_data->output[emit_data->chan] = lp_build_shr(uint_bld, emit_data->args[0],
+ masked_count);
}
/* TGSI_OPCODE_ISLT (CPU Only) */