[PATCH 11/16] cast: simplify [ZS]EXT(AND(x,M),N)

[Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>]

A OP_AND with a constant value followed by a sign or zero-extension
can often be moved after the extension.

This is good because it can trigger the cancellation of the OP[ZS]EXT
with a preceding OP_TRUNC, a common situation with bitfields.

Note: This 'simplification' is less desirable if there is
      no preceding OP_TRUNC, for example, in a sequence like:
		and.32	%t <- %a, $mask
		*ext.64 %r <- %t
      If needed, this can be filtered out at some later stage.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
 simplify.c                         | 24 ++++++++++++++++++++++++
 validation/optim/and-extend.c      |  1 -
 validation/optim/and-extendx.c     |  1 -
 validation/optim/trunc-mask-zext.c |  1 -
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/simplify.c b/simplify.c
index 336339fac..a0f7aa327 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1011,6 +1011,30 @@ static int simplify_cast(struct instruction *insn)
 			mask &= (1ULL << size) - 1;
 			insn->src2 = value_pseudo(mask);
 			return REPEAT_CSE;
+
+		case OP_SEXT:
+			if (val->value & (1 << (def->size - 1)))
+				break;
+			// OK, sign bit is 0
+		case OP_ZEXT:
+			if (nbr_users(src) > 1)
+				break;
+			// transform:
+			//	and.n	%b <- %a, M
+			//	*ext.m	%c <- (n) %b
+			// into:
+			//	zext.m	%b <- %a
+			//	and.m	%c <- %b, M
+			// For ZEXT, the mask will always be small
+			// enough. For SEXT, it can only be done if
+			// the mask force the sign bit to 0.
+			def->opcode = OP_ZEXT;
+			def->orig_type = insn->orig_type;
+			def->type = insn->type;
+			def->size = insn->size;
+			insn->opcode = OP_AND;
+			insn->src2 = val;
+			return REPEAT_CSE;
 		}
 		break;
 	case OP_TRUNC:
diff --git a/validation/optim/and-extend.c b/validation/optim/and-extend.c
index fdcf470f0..eb5892369 100644
--- a/validation/optim/and-extend.c
+++ b/validation/optim/and-extend.c
@@ -18,7 +18,6 @@ u32 sfoo(u32 x)
 /*
  * check-name: and-extend
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-excludes: trunc\\.
diff --git a/validation/optim/and-extendx.c b/validation/optim/and-extendx.c
index a580bd0d6..5c181c933 100644
--- a/validation/optim/and-extendx.c
+++ b/validation/optim/and-extendx.c
@@ -18,7 +18,6 @@ u64 sfoo(int x)
 /*
  * check-name: and-extend
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-contains: and\\.64.*0x7fff
diff --git a/validation/optim/trunc-mask-zext.c b/validation/optim/trunc-mask-zext.c
index 30ae5aeeb..9b6041746 100644
--- a/validation/optim/trunc-mask-zext.c
+++ b/validation/optim/trunc-mask-zext.c
@@ -6,7 +6,6 @@ unsigned long long foo(unsigned long long x)
 /*
  * check-name: trunc-mask-zext
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-excludes: trunc\\.
-- 
2.18.0

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